Application that crashed: kontact
Version of the application: 4.3.1
KDE Version: 4.3.1 (KDE 4.3.1)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-11-generic i686
Distribution: Ubuntu karmic (development branch)

What I was doing when the application crashed:
Kmail and Kontact  (when kmail is installed) crash at startup. 
 kontact

This happens every time with this version 

Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
Calling appendChild() on a null node does nothing.
<unknown program name>(6374)/: Communication problem with  "kontact" , it probably crashed.
Error message was:  "org.freedesktop.DBus.Error.NoReply" : " "Message did not receive a reply (timeout by message bus)" "

KCrash: Application 'kontact' crashing...
sock_file=/home/vasile/.kde/socket-susinpoala/kdeinit4__0


 -- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault
[KCrash Handler]
#6  0xb5008612 in QListData::begin (this=0x0, folderId=..., id=0, dir=0xc) at /usr/include/qt4/QtCore/qlist.h:90
#7  QList<KMFolderNode*>::constBegin (this=0x0, folderId=..., id=0, dir=0xc) at /usr/include/qt4/QtCore/qlist.h:239
#8  KMFolderMgr::findIdString (this=0x0, folderId=..., id=0, dir=0xc) at ../../kmail/kmfoldermgr.cpp:241
#9  0xb50dea35 in KMKernel::findFolderById (this=0xa3df3f8, idString=...) at ../../kmail/kmkernel.cpp:2295
#10 0xb51e3a65 in KMSearch::read (this=0xa55e5c8, location=...) at ../../kmail/kmfoldersearch.cpp:122
#11 0xb51e4234 in KMFolderSearch::readSearch (this=0xa485400) at ../../kmail/kmfoldersearch.cpp:522
#12 0xb51e54aa in KMFolderSearch::open (this=0xa485400) at ../../kmail/kmfoldersearch.cpp:534
#13 0xb4fdcea6 in FolderStorage::countUnread (this=0xa485400) at ../../kmail/folderstorage.cpp:872
#14 0xb4faae9d in KMFolder::updateIndicatorCount (this=0xa494100) at ../../kmail/kmfolder.cpp:989
#15 0xb4fb18b8 in KMFolder::readConfig (this=0xa494100, configGroup=...) at ../../kmail/kmfolder.cpp:222
#16 0xb4fe1577 in FolderStorage::readConfig (this=0xa485400) at ../../kmail/folderstorage.cpp:963
#17 0xb4fb00a8 in KMFolder (this=0xa494100, aParent=0xa48b374, aFolderName=..., aFolderType=KMFolderTypeSearch, withIndex=true, exportedSernums=true) at ../../kmail/kmfolder.cpp:149
#18 0xb5005dfa in KMFolderDir::reload (this=0xa48b374) at ../../kmail/kmfolderdir.cpp:313
#19 0xb500af76 in KMFolderMgr::setBasePath (this=0xa48b368, aBasePath=...) at ../../kmail/kmfoldermgr.cpp:164
#20 0xb500b409 in KMFolderMgr (this=0xa48b368, aBasePath=..., dirType=KMSearchDir) at ../../kmail/kmfoldermgr.cpp:45
#21 0xb50f0cc7 in KMKernel::init (this=0xa3df3f8) at ../../kmail/kmkernel.cpp:1482
#22 0x0256d91b in KMailPart (this=0xa347048, parentWidget=0xa0074c8, parent=0xa0074c8, __in_chrg=<value optimized out>, __vtt_parm=<value optimized out>) at ../../kmail/kmail_part.cpp:73
#23 0x0256efb2 in KPluginFactory::createPartInstance<KMailPart> (parentWidget=0xa0074c8, parent=0xa0074c8, args=...) at /usr/include/kpluginfactory.h:467
#24 0x05e8eec5 in KPluginFactory::create (this=0xa34d948, iface=0x238900 "KParts::ReadOnlyPart", parentWidget=0xa0074c8, parent=0xa0074c8, args=..., keyword=...)
    at ../../kdecore/util/kpluginfactory.cpp:191
#25 0x00a5fa84 in KPluginFactory::create<KParts::ReadOnlyPart> (this=0xa0074c8, libname=0xa1e0cb8 "kmailpart") at /usr/include/kpluginfactory.h:491
#26 Kontact::Core::createPart (this=0xa0074c8, libname=0xa1e0cb8 "kmailpart") at ../../kontactinterfaces/core.cpp:87
#27 0x00a607b7 in Kontact::Plugin::loadPart (this=0xa330610) at ../../kontactinterfaces/plugin.cpp:148
#28 0x03259795 in KMailPlugin::createPart (this=0xa330610) at ../../../../kontact/plugins/kmail/kmail_plugin.cpp:170
#29 0x00a60713 in Kontact::Plugin::part (this=0xa330610) at ../../kontactinterfaces/plugin.cpp:187
#30 0x00f4d68c in Kontact::MainWindow::selectPlugin (this=0xa0074c8, plugin=0xa330610) at ../../../kontact/src/mainwindow.cpp:754
#31 0x00f4875c in Kontact::MainWindow::loadSettings (this=0xa0074c8) at ../../../kontact/src/mainwindow.cpp:926
#32 0x00f51c51 in Kontact::MainWindow::initObject (this=0xa0074c8) at ../../../kontact/src/mainwindow.cpp:226
#33 0x00f520ed in MainWindow (this=0xa0074c8, __in_chrg=<value optimized out>, __vtt_parm=<value optimized out>) at ../../../kontact/src/mainwindow.cpp:162
#34 0x0804be1e in KontactApp::newInstance (this=0xbfa8fdf4) at ../../../kontact/src/main.cpp:134
#35 0x0044a700 in KUniqueApplicationAdaptor::newInstance (this=0xa1bbee8, asn_id=..., args=...) at ../../kdeui/kernel/kuniqueapplication.cpp:459
#36 0x0044ae12 in KUniqueApplicationAdaptor::qt_metacall (this=0xa1bbee8, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0xbfa8f41c) at ./kuniqueapplication_p.moc:75
#37 0x009377b4 in QDBusConnectionPrivate::deliverCall (this=0x9ff2c88, object=0xa1bbee8, msg=..., metaTypes=..., slotIdx=4) at qdbusintegrator.cpp:891
#38 0x0093895d in QDBusConnectionPrivate::activateCall (this=0x9ff2c88, object=0xa1bbee8, flags=337, msg=...) at qdbusintegrator.cpp:796
#39 0x00939234 in QDBusConnectionPrivate::activateObject (this=0x9ff2c88, node=..., msg=..., pathStartPos=16) at qdbusintegrator.cpp:1347
#40 0x009394da in QDBusActivateObjectEvent::placeMetaCall (this=0xa1d28b8) at qdbusintegrator.cpp:1464
#41 0x0079c5ee in QObject::event (this=0xbfa8fdf4, e=0xa1d28b8) at kernel/qobject.cpp:1111
#42 0x0078bfeb in QCoreApplication::event (this=0xbfa8fdf4, e=0xa1d28b8) at kernel/qcoreapplication.cpp:1434
#43 0x0108a996 in QApplication::event (this=0xbfa8fdf4, e=0xa1d28b8) at kernel/qapplication.cpp:2317
#44 0x01084f44 in QApplicationPrivate::notify_helper (this=0x9ffa340, receiver=0xbfa8fdf4, e=0xa1d28b8) at kernel/qapplication.cpp:4056
#45 0x0108c66c in QApplication::notify (this=0xbfa8fdf4, receiver=0xbfa8fdf4, e=0xa1d28b8) at kernel/qapplication.cpp:3603
#46 0x00442f8a in KApplication::notify (this=0xbfa8fdf4, receiver=0xbfa8fdf4, event=0xa1d28b8) at ../../kdeui/kernel/kapplication.cpp:302
#47 0x0078c6bb in QCoreApplication::notifyInternal (this=0xbfa8fdf4, receiver=0xbfa8fdf4, event=0xa1d28b8) at kernel/qcoreapplication.cpp:610
#48 0x0078d2a2 in QCoreApplication::sendEvent (receiver=0x0, event_type=0, data=0x9fda820) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#49 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x9fda820) at kernel/qcoreapplication.cpp:1247
#50 0x0078d46d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1140
#51 0x007b73ef in QCoreApplication::sendPostedEvents (s=0x9ffc310) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#52 postEventSourceDispatch (s=0x9ffc310) at kernel/qeventdispatcher_glib.cpp:210
#53 0x08e37e78 in g_main_dispatch (context=0x9ffc290) at /build/buildd/glib2.0-2.22.0/glib/gmain.c:1960
#54 IA__g_main_context_dispatch (context=0x9ffc290) at /build/buildd/glib2.0-2.22.0/glib/gmain.c:2513
#55 0x08e3b720 in g_main_context_iterate (context=0x9ffc290, block=<value optimized out>, dispatch=1, self=0x9ff70a0) at /build/buildd/glib2.0-2.22.0/glib/gmain.c:2591
#56 0x08e3b853 in IA__g_main_context_iteration (context=0x9ffc290, may_block=1) at /build/buildd/glib2.0-2.22.0/glib/gmain.c:2654
#57 0x007b701c in QEventDispatcherGlib::processEvents (this=0x9fda9f8, flags=...) at kernel/qeventdispatcher_glib.cpp:327
#58 0x01125ad5 in QGuiEventDispatcherGlib::processEvents (this=0x9fda9f8, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#59 0x0078ac69 in QEventLoop::processEvents (this=0xbfa8fd54, flags=) at kernel/qeventloop.cpp:149
#60 0x0078b0ba in QEventLoop::exec (this=0xbfa8fd54, flags=...) at kernel/qeventloop.cpp:201
#61 0x0078d52f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#62 0x01084dc7 in QApplication::exec () at kernel/qapplication.cpp:3525
#63 0x0804b506 in main (argc=1, argv=0xbfa90014) at ../../../kontact/src/main.cpp:218

Reported using DrKonqi