Removing the configuration file and all related directories in  ~/.kde/share/apps produces a crash at the moment the jabber account is configured and used for the first time. 

The backtrace is slightly different from the one obtained when starting a pre-configured instance, so I'll include it here:

Backtrace:
Application: Kopete (kopete), signal: Segmentation fault
[KCrash Handler]
#6  0x001d69ca in Kopete::Contact::account() const () from /usr/lib/libkopete.so.4
#7  0x001d72ec in Kopete::Contact::isOnline() const () from /usr/lib/libkopete.so.4
#8  0x001b8eaa in Kopete::Account::isConnected() const () from /usr/lib/libkopete.so.4
#9  0x030da928 in ?? () from /usr/lib/kde4/kopete_jabber.so
#10 0x002083dc in Kopete::PasswordedAccount::connect(Kopete::OnlineStatus const&) () from /usr/lib/libkopete.so.4
#11 0x00114d6b in AddAccountWizard::accept() () from /usr/lib/libkopeteaddaccountwizard.so.1
#12 0x018fb226 in QDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libQtGui.so.4
#13 0x0101a49a in KDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#14 0x010f62aa in KPageDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#15 0x01002c7a in KAssistantDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#16 0x00114b2a in AddAccountWizard::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkopeteaddaccountwizard.so.1
#17 0x047de11a in QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) () from /usr/lib/libQtCore.so.4
#18 0x047ec89b in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#19 0x01016037 in KDialog::user1Clicked() () from /usr/lib/libkdeui.so.5
#20 0x0101853e in KDialog::slotButtonClicked(int) () from /usr/lib/libkdeui.so.5
#21 0x0101a819 in KDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#22 0x010f62aa in KPageDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#23 0x01002c7a in KAssistantDialog::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkdeui.so.5
#24 0x00114b2a in AddAccountWizard::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libkopeteaddaccountwizard.so.1
#25 0x047de11a in QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) () from /usr/lib/libQtCore.so.4
#26 0x047ec89b in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#27 0x047f2053 in QSignalMapper::mapped(int) () from /usr/lib/libQtCore.so.4
#28 0x047f32cd in QSignalMapper::map(QObject*) () from /usr/lib/libQtCore.so.4
#29 0x047f34ae in QSignalMapper::map() () from /usr/lib/libQtCore.so.4
#30 0x047f357b in QSignalMapper::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libQtCore.so.4
#31 0x047de11a in QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) () from /usr/lib/libQtCore.so.4
#32 0x047ec89b in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#33 0x01ae4789 in QAbstractButton::clicked(bool) () from /usr/lib/libQtGui.so.4
#34 0x017c7519 in ?? () from /usr/lib/libQtGui.so.4
#35 0x017c8364 in ?? () from /usr/lib/libQtGui.so.4
#36 0x017c8611 in QAbstractButton::mouseReleaseEvent(QMouseEvent*) () from /usr/lib/libQtGui.so.4
#37 0x0141df9e in QWidget::event(QEvent*) () from /usr/lib/libQtGui.so.4
#38 0x017c73be in QAbstractButton::event(QEvent*) () from /usr/lib/libQtGui.so.4
#39 0x01870b12 in QPushButton::event(QEvent*) () from /usr/lib/libQtGui.so.4
#40 0x013c119c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#41 0x013c876b in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#42 0x010b567a in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#43 0x047d8eab in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#44 0x013c771f in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /usr/lib/libQtGui.so.4
#45 0x01450d18 in ?? () from /usr/lib/libQtGui.so.4
#46 0x014501f1 in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/libQtGui.so.4
#47 0x0147f04a in ?? () from /usr/lib/libQtGui.so.4
#48 0x044e4e88 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#49 0x044e8730 in ?? () from /lib/libglib-2.0.so.0
#50 0x044e8863 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#51 0x04804bd5 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#52 0x0147eb75 in ?? () from /usr/lib/libQtGui.so.4
#53 0x047d74c9 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#54 0x047d791a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#55 0x047dbb0f in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#56 0x013c1237 in QApplication::exec() () from /usr/lib/libQtGui.so.4
#57 0x08059a8c in _start ()

Could you start Kopete from console with "valgrind kopete --nofork" and paste here the log

==1396== Memcheck, a memory error detector
==1396== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==1396== Using Valgrind-3.5.0-Debian and LibVEX; rerun with -h for copyright info
==1396== Command: kopete --nofork
==1396== 
==1396== Conditional jump or move depends on uninitialised value(s)
==1396==    at 0x5160EC0: ??? (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x516D58A: ??? (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x50AA8C3: ??? (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x50AA98B: ??? (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x50B590E: QPainter::drawLines(QLineF const*, int) (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x769C6D0: ??? (in /usr/lib/kde4/plugins/styles/oxygen.so)
==1396==    by 0x76930E3: ??? (in /usr/lib/kde4/plugins/styles/oxygen.so)
==1396==    by 0x4CFD119: QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x4D00F54: QMetaMethod::invoke(QObject*, Qt::ConnectionType, QGenericReturnArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument) const (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x4D0155E: QMetaObject::invokeMethod(QObject*, char const*, Qt::ConnectionType, QGenericReturnArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x5268E8B: QStyle::standardIcon(QStyle::StandardPixmap, QStyleOption const*, QWidget const*) const (in /usr/lib/libQtGui.so.4.6.0)
==1396==    by 0x53E9B91: ??? (in /usr/lib/libQtGui.so.4.6.0)
==1396== 
kopete(1396)/libkopete KopeteSystemTray::KopeteSystemTray:
kopete(1396)/kdecore (KSycoca) KSycocaPrivate::openDatabase: Trying to open ksycoca from  "/var/tmp/kdecache-janwillem/ksycoca4"
kopete(1396)/kdepimlibs (kabc) KABC::StdAddressBook::self:
kopete(1396)/kdepimlibs (kabc) KABC::StdAddressBook::self: asynchronous= false
kopete(1396)/kresources KRES::Factory::self:
kopete(1396)/kresources KRES::ManagerImpl::ManagerImpl:
kopete(1396)/kresources KRES::ManagerImpl::readConfig:
kopete(1396)/kresources KRES::Factory::self:
kopete(1396)/kresources KRES::ManagerImpl::readResourceConfig: "yPYF1dmPAy"
kopete(1396)/kresources KRES::Factory::Private::resourceInternal: ( "akonadi" , config )
kopete(1396)/kresources ResourcePrivateBase::ResourcePrivateBase: read MIME config pair: mimeType= "text/directory" , url= KUrl("akonadi:?collection=5")
kopete(1396)/kresources ResourcePrivateBase::ResourcePrivateBase: read MIME config pair: mimeType= "application/x-vnd.kde.contactgroup" , url= KUrl("akonadi:?collection=5")
kopete(1396)/kresources KRES::ManagerImpl::readResourceConfig: "RnVLTnIKnM"
kopete(1396)/kresources KRES::Factory::Private::resourceInternal: ( "file" , config )
kopete(1396)/kdepimlibs (kabc) KABC::FormatFactory::self:
kopete(1396)/kdepimlibs (kabc) KABC::StdAddressBook::StdAddressBook:
kopete(1396)/kdepimlibs (kabc) KABC::StdAddressBook::self: calling init after instance creation
kopete(1396)/kresources KRES::Resource::open: Opening resource "kde4-akonadi"
kopete(1396)/kresources ResourcePrivateBase::doOpen:
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::openResource:
kopete(1396)/kresources KRES::Resource::open: Opening resource "Default Address Book"
kopete(1396)/kresources KRES::ManagerImpl::writeConfig:
kopete(1396)/kresources KRES::ManagerImpl::writeResourceConfig: Saving resource "yPYF1dmPAy"
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::writeConfig:
kopete(1396)/kresources KRES::Resource::writeConfig:
kopete(1396)/kresources ResourcePrivateBase::writeConfig: wrote MIME config pair: mimeType= "text/directory" , url= KUrl("akonadi:?collection=5")
kopete(1396)/kresources ResourcePrivateBase::writeConfig: wrote MIME config pair: mimeType= "application/x-vnd.kde.contactgroup" , url= KUrl("akonadi:?collection=5")
kopete(1396)/kresources KRES::ManagerImpl::writeResourceConfig: Saving resource "RnVLTnIKnM"
kopete(1396)/kresources KRES::Resource::writeConfig:
kopete(1396)/kresources KRES::ManagerImpl::writeConfig: Saving general info
kopete(1396)/kresources KRES::ManagerImpl::writeConfig: finished
kopete(1396)/kdepimlibs (kabc) KABC::AddressBook::load:
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::clearResource:
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::load:
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::clearResource:
kopete(1396)/kresources ResourcePrivateBase::doLoad: isLoading= false
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::subResourceAdded: id= "akonadi:?collection=9"
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::addresseeAdded: Addressee (uid= "0DWfpeLhZ9" , name= "xxx" ), subResource= "akonadi:?collection=9"
... 
kopete(1396)/kdepimlibs (kabc) KABC::ResourceAkonadi::Private::addresseeAdded: Addressee (uid= "zq9gsruYZs" , name= "xxx" ), subResource= "akonadi:?collection=9"
kopete(1396)/kdepimlibs (kabc) KABC::ResourceFile::load: "/data/users/janwillem/ubuntu/.kde/share/apps/kabc/std.vcf" '
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 19 (X_DeleteProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 19 (X_DeleteProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 8 (X_MapWindow)
  Resource id:  0x400003a
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 18 (X_ChangeProperty)
  Resource id:  0x400003a
X Error: RenderBadPicture (invalid Picture parameter) 158
  Extension:    148 (RENDER)
  Minor opcode: 7 (RenderFreePicture)
  Resource id:  0x400003b
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 4 (X_DestroyWindow)
  Resource id:  0x400003a
kopete(1396)/kutils (KSettings::Dispatcher) KSettings::Dispatcher::registerComponent: "kopete_emailwindow"
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Successfully loaded plugin ' "kopete_emailwindow" '
Calling appendChild() on a null node does nothing.
kopete(1396)/kutils (KSettings::Dispatcher) KSettings::Dispatcher::registerComponent: "kopete_indicator"
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Successfully loaded plugin ' "kopete_indicator" '
Calling appendChild() on a null node does nothing.
kopete(1396)/kdecore (KLibrary) kde4Factory: The library "/usr/lib/kde4/kopete_history.so" does not offer a qt_plugin_instance function.
kopete(1396)/kutils (KSettings::Dispatcher) KSettings::Dispatcher::registerComponent: "kopete_history"
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Successfully loaded plugin ' "kopete_history" '
kopete(1396)/kutils (KSettings::Dispatcher) KSettings::Dispatcher::registerComponent: "kopete_chatwindow"
kopete(1396)/kio (KDirListerCache) KDirListerCache::listDir: Listing directory: KUrl("file:///usr/share/kde4/apps/kopete/styles")
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Successfully loaded plugin ' "kopete_chatwindow" '
Calling appendChild() on a null node does nothing.
kopete(1396)/kutils (KSettings::Dispatcher) KSettings::Dispatcher::registerComponent: "kopete_jabber"
kopete(1396)/kopete (jabber) JabberProtocol::JabberProtocol: [JabberProtocol] Loading ...
kopete(1396)/libkopete Kopete::MimeTypeHandler::registerAsProtocolHandler: Mime type  "xmpp"  registered
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Successfully loaded plugin ' "kopete_jabber" '
Calling appendChild() on a null node does nothing.
kopete(1396)/libkopete Kopete::AccountManager::slotPluginLoaded: Creating account for ' "janwillem.vandemeent@gmail.com" '
kopete(1396)/kopete (jabber) JabberProtocol::createNewAccount: Create New Account. ID:  "janwillem.vandemeent@gmail.com"
kopete(1396)/kopete (jabber) JabberAccount::JabberAccount: Instantiating new account  "janwillem.vandemeent@gmail.com"
kopete(1396)/kopete (jabber) JabberContactPool::addContact: Adding new contact  "janwillem.vandemeent@gmail.com"
kopete(1396)/kopete (jabber) JabberBaseContact::updateContact: Synchronizing local copy of  "janwillem.vandemeent@gmail.com"  with information received from server.  (name=' "" ' groups=' () ')
kopete(1396)/kopete (jabber) JabberContact::JabberContact: "janwillem.vandemeent@gmail.com"   is created  -  JabberContact(0x7dd4238)
kopete(1396)/libkopete Kopete::PluginManager::loadPluginInternal: Unable to find a plugin named ' "" '! 
kopete(1396)/kio (Slave) KIO::Slave::createSlave: createSlave "file" for KUrl("file:///usr/share/kde4/apps/kopete/styles")
kopete(1396)/kio (KIOConnection) KIO::ConnectionServer::listenForRemote: Listening on  "local:/tmp/ksocket-janwillem/kopetemK1396.slave-socket"
kopete(1396)/kopete (jabber) JabberResourcePool::bestJabberResource: Determining best resource for  "janwillem.vandemeent@gmail.com"
kopete(1396)/kopete (jabber) JabberResourcePool::lockedJabberResource: No lock available for  "janwillem.vandemeent@gmail.com"
kopete(1396)/kopete (jabber) JabberAccount::connectWithPassword: called
==1396== Use of uninitialised value of size 4
==1396==    at 0x415C97A: Kopete::Account::myself() const (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0xBA38927: ??? (in /usr/lib/kde4/kopete_jabber.so)
==1396==    by 0x41AC3DB: Kopete::PasswordedAccount::connect(Kopete::OnlineStatus const&) (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0xBA386B1: ??? (in /usr/lib/kde4/kopete_jabber.so)
==1396==    by 0x4163085: Kopete::AccountManager::setOnlineStatus(unsigned int, Kopete::StatusMessage const&, unsigned int) (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x805B0AB: ??? (in /usr/bin/kopete)
==1396==    by 0x805B1EC: ??? (in /usr/bin/kopete)
==1396==    by 0x4CFD119: QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x4D0B89A: QMetaObject::activate(QObject*, QMetaObject const*, int, void**) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x41AE186: Kopete::PluginManager::allPluginsLoaded() (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x41B0DD2: Kopete::PluginManager::slotLoadNextPlugin() (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x41B431A: Kopete::PluginManager::qt_metacall(QMetaObject::Call, int, void**) (in /usr/lib/libkopete.so.4.4.0)
==1396== 
==1396== Invalid read of size 4
==1396==    at 0x417A9CA: Kopete::Contact::account() const (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x417B2EB: Kopete::Contact::isOnline() const (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x415CEA9: Kopete::Account::isConnected() const (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0xBA38927: ??? (in /usr/lib/kde4/kopete_jabber.so)
==1396==    by 0x41AC3DB: Kopete::PasswordedAccount::connect(Kopete::OnlineStatus const&) (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0xBA386B1: ??? (in /usr/lib/kde4/kopete_jabber.so)
==1396==    by 0x4163085: Kopete::AccountManager::setOnlineStatus(unsigned int, Kopete::StatusMessage const&, unsigned int) (in /usr/lib/libkopete.so.4.4.0)
==1396==    by 0x805B0AB: ??? (in /usr/bin/kopete)
==1396==    by 0x805B1EC: ??? (in /usr/bin/kopete)
==1396==    by 0x4CFD119: QMetaObject::metacall(QObject*, QMetaObject::Call, int, void**) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x4D0B89A: QMetaObject::activate(QObject*, QMetaObject const*, int, void**) (in /usr/lib/libQtCore.so.4.6.0)
==1396==    by 0x41AE186: Kopete::PluginManager::allPluginsLoaded() (in /usr/lib/libkopete.so.4.4.0)
==1396==  Address 0x8 is not stack'd, malloc'd or (recently) free'd
==1396== 
KCrash: Application 'kopete' crashing...
==1396== 
==1396== HEAP SUMMARY:
==1396==     in use at exit: 4,961,556 bytes in 68,148 blocks
==1396==   total heap usage: 648,612 allocs, 580,464 frees, 165,411,401 bytes allocated
==1396== 
==1396== LEAK SUMMARY:
==1396==    definitely lost: 3,369 bytes in 17 blocks
==1396==    indirectly lost: 11,312 bytes in 568 blocks
==1396==      possibly lost: 3,392,867 bytes in 48,160 blocks
==1396==    still reachable: 1,554,008 bytes in 19,403 blocks
==1396==         suppressed: 0 bytes in 0 blocks
==1396== Rerun with --leak-check=full to see details of leaked memory
==1396== 
==1396== For counts of detected and suppressed errors, rerun with: -v
==1396== Use --track-origins=yes to see where uninitialised values come from
==1396== ERROR SUMMARY: 9 errors from 3 contexts (suppressed: 260 from 15)

Please check if /usr/lib/kde4/kopete_jabber.so isn't from older Kopete version

Gah -- my bad! Failed to check.

> dpkg -l |grep kopete
ii  kopete                                     4:4.3.3-0ubuntu1~ppa2                                       
ii  libkopete4                                 4:4.3.90-0ubuntu1~karmic1~ppa1                              

Apparently kubuntu failed to ship the latest kopete version with the KDE 4.4 RC1 packages. This should be resolved when i update kopete to 4.3.90 right?

Yes most likely, also don't forget to update the protocols if Ubuntu has separate package for them.