Version:           0.50.1 (using 4.0.3 (KDE 4.0.3), Kubuntu packages)
Compiler:          gcc
OS:                Linux (i686) release 2.6.24-19-generic

Somehow my friend's Kopete got into a mode, where attempt to talk to ANYONE causes an immediate crash. The following appears on stderr:

QEventDispatcherUNIX::unregisterTimer: invalid argument
QObject::connect: Connecting from COMPAT signal (KAction::activated())
kopete(16818) Kopete::IdentityManager::load: Created identity  "uqh1MNe3m3"
Object::connect: No such signal Client::chatRoomConnected(WORD,QString)
Object::connect:  (sender name:   'oscarclient')
kopete(16818) Kopete::AccountManager::setOnlineStatus: category:  2 , Kopete::OnlineStatusManager::Away:  4
kopete(16818) KRichTextEditPart::readConfig: Text color:  "#000000"
kopete(16818) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_hspell.desktop"
kopete(16818) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_enchant.desktop"
kopete(16818) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_aspell.desktop"
Couldn't create speller for "uk" :  /home/n/.aspell.uk.pws: The word "KHTML" is invalid. The character 'K' (U+4B) may not appear at the beginning of a word. 
ASSERT: "dict" in file /build/buildd/kde4libs-4.0.3/kdecore/sonnet/loader.cpp, line 116
KCrash: crashing... crashRecursionCounter = 2
KCrash: Application Name = kopete path = <unknown> pid = 16818
sock_file=/home/n/.kde4/socket-thinkpad/kdeinit4__0

and the stack is thus:

(no debugging symbols found)
[...]
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread 0xb5882740 (LWP 16818)]
[New Thread 0xb37bcb90 (LWP 16885)]
(no debugging symbols found)
[...]
(no debugging symbols found)
[KCrash handler]
#6  0xb7f13410 in __kernel_vsyscall ()
#7  0xb6810085 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb6811a01 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb7dbea75 in qt_message_output () from /usr/lib/libQtCore.so.4
#10 0xb7dbeb38 in qFatal () from /usr/lib/libQtCore.so.4
#11 0xb7dbecd5 in qt_assert () from /usr/lib/libQtCore.so.4
#12 0xb7cd83b2 in Sonnet::Loader::createSpeller ()
   from /usr/lib/kde4/lib/libkdecore.so.5
#13 0xb7cdab7a in ?? () from /usr/lib/kde4/lib/libkdecore.so.5
#14 0xb7a746bc in Sonnet::Highlighter::Highlighter ()
   from /usr/lib/kde4/lib/libkdeui.so.5
#15 0xb3962ab3 in ChatTextEditPart::ChatTextEditPart ()
   from /usr/lib/kde4/lib/libkopetechatwindow_shared.so.1
#16 0xb39892e8 in ?? () from /usr/lib/kde4/lib/kde4/kopete_chatwindow.so
#17 0xb398973b in ?? () from /usr/lib/kde4/lib/kde4/kopete_chatwindow.so
#18 0xb6eba100 in KopeteViewManager::view ()
   from /usr/lib/kde4/lib/libkopete.so.4
#19 0xb6ef73af in Kopete::ChatSessionManager::createView ()
   from /usr/lib/kde4/lib/libkopete.so.4
#20 0xb6ef3fe4 in Kopete::ChatSession::view ()
   from /usr/lib/kde4/lib/libkopete.so.4
#21 0xb6eff3de in Kopete::Contact::execute ()
   from /usr/lib/kde4/lib/libkopete.so.4
#22 0x08070865 in ?? ()
#23 0x08072d76 in ?? ()
#24 0xb7e8dcf4 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#25 0xb7e8e8c2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#26 0xb6b81f0f in K3ListView::executed ()
   from /usr/lib/kde4/lib/libkde3support.so.4
#27 0xb6b870ed in K3ListView::emitExecute ()
   from /usr/lib/kde4/lib/libkde3support.so.4
#28 0xb6b87147 in K3ListView::slotMouseButtonClicked ()
   from /usr/lib/kde4/lib/libkde3support.so.4
#29 0xb6b87d35 in K3ListView::qt_metacall ()
   from /usr/lib/kde4/lib/libkde3support.so.4
#30 0xb6ece64a in Kopete::UI::ListView::ListView::qt_metacall ()
   from /usr/lib/kde4/lib/libkopete.so.4
#31 0x08072c4f in ?? ()
#32 0xb7e8dcf4 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#33 0xb7e8e8c2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#34 0xb6e196f5 in Q3ListView::mouseButtonClicked ()
   from /usr/lib/libQt3Support.so.4
#35 0xb6cc9763 in Q3ListView::contentsMouseReleaseEventEx ()
   from /usr/lib/libQt3Support.so.4
#36 0xb6cc9b54 in Q3ListView::contentsMouseReleaseEvent ()
   from /usr/lib/libQt3Support.so.4
#37 0xb6b865dc in K3ListView::contentsMouseReleaseEvent ()
   from /usr/lib/kde4/lib/libkde3support.so.4
#38 0xb6d22d98 in Q3ScrollView::viewportMouseReleaseEvent ()
   from /usr/lib/libQt3Support.so.4
#39 0xb6d23e98 in Q3ScrollView::eventFilter ()
   from /usr/lib/libQt3Support.so.4
#40 0xb6cce616 in Q3ListView::eventFilter () from /usr/lib/libQt3Support.so.4
#41 0xb6ecd27c in Kopete::UI::ListView::ListView::eventFilter ()
   from /usr/lib/kde4/lib/libkopete.so.4
#42 0xb70a6242 in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#43 0xb70aa4f1 in QApplication::notify () from /usr/lib/libQtGui.so.4
#44 0xb7a1fce3 in KApplication::notify () from /usr/lib/kde4/lib/libkdeui.so.5
#45 0xb7e7ac1b in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#46 0xb7102b4a in ?? () from /usr/lib/libQtGui.so.4
#47 0xb7102197 in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#48 0xb7127684 in ?? () from /usr/lib/libQtGui.so.4
#49 0xb671dbf8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#50 0xb6720e5e in ?? () from /usr/lib/libglib-2.0.so.0
#51 0xb67213ac in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#52 0xb7e9ef82 in QEventDispatcherGlib::processEvents ()
   from /usr/lib/libQtCore.so.4
#53 0xb7127475 in ?? () from /usr/lib/libQtGui.so.4
#54 0xb7e79fb2 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#55 0xb7e7a0bc in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#56 0xb7e7c88a in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#57 0xb70a56e7 in QApplication::exec () from /usr/lib/libQtGui.so.4
#58 0x080872fb in ?? ()
#59 0xb67fb450 in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#60 0x080637b1 in _start ()
#0  0xb7f13410 in __kernel_vsyscall ()

Upon moving the "offending" /home/n/.aspell.uk.pws aside, the problem goes away -- the stderr changes to:
kopete(17097) Kopete::AccountManager::setOnlineStatus: category:  2 , Kopete::OnlineStatusManager::Away:  4
kopete(17097) KRichTextEditPart::readConfig: Text color:  "#000000"
kopete(17097) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_hspell.desktop"
kopete(17097) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_enchant.desktop"
kopete(17097) Sonnet::Loader::loadPlugin: Successfully loaded plugin: "kspell_aspell.desktop"
Enchant dict for "uk" 0x8cc09c0 
kopete(17097) KRichTextEditPart::readConfig: Text color:  "#000000"
kopete(17097) Sonnet::Highlighter::slotRehighlight: Highlighter::slotRehighlight()

and the chat-windows open up fine.

I don't know, what's "wrong" with .aspell.uk.pws -- it just had a handful of words (in ASCII, rather than Cyrillic, however). But whatever unhappiness it may have caused the dictionary (enchant?), it should never be causing a crash, should it?