Application: kwin (4.4.00 (KDE 4.4.0))
KDE Platform Version: 4.4.00 (KDE 4.4.0)
Qt Version: 4.6.2
Operating System: Linux 2.6.31.12-174.2.22.fc12.i686.PAE i686
Distribution: "Fedora release 12 (Constantine)"

-- Information about the crash:
When I use a keyboard shotcut, which was set to ctrl + tab for desktop switchin in System Settings, the whole screen goes something like  merge of all desktops. Window decoractions went disabled, leaving only interior of the windows.  

The whole situation last sth about a second or two, during this time - the whole system freezes, no other shorcuts worked etc, then I saw the Bug Report window with everything working properly. No application were closed or disturbed in any way.

This phenomena occurs either on both of my monitors and on a single laptop monitor.

The crash can be reproduced some of the time.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  0x00000010 in ?? ()
#7  0x067b038b in KWin::TabBox::ClientModel::data (this=0x90fa648, index=..., role=37) at /usr/src/debug/kdebase-workspace-4.4.0/kwin/tabbox/clientmodel.cpp:77
#8  0x067b563a in KWin::TabBox::TabBoxHandlerPrivate::updateHighlightWindows (this=0x90fc940) at /usr/src/debug/kdebase-workspace-4.4.0/kwin/tabbox/tabboxhandler.cpp:237
#9  0x067aa185 in KWin::TabBox::TabBox::show (this=0x9142d80) at /usr/src/debug/kdebase-workspace-4.4.0/kwin/tabbox.cpp:458
#10 0x067aa1e2 in KWin::TabBox::TabBox::qt_metacall (this=0x9142d80, _c=InvokeMetaMethod, _id=<value optimized out>, _a=0xbfd88fdc)
    at /usr/src/debug/kdebase-workspace-4.4.0/i686-redhat-linux-gnu/kwin/tabbox.moc:72
#11 0x053915db in QMetaObject::metacall (object=0x9142d80, cl=InvokeMetaMethod, idx=4, argv=0xbfd88fdc) at kernel/qmetaobject.cpp:237
#12 0x053a04af in QMetaObject::activate (sender=0x9142dac, m=0x54a0704, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3293
#13 0x053e8298 in QTimer::timeout (this=0x9142dac) at .moc/release-shared/moc_qtimer.cpp:134
#14 0x053a637e in QTimer::timerEvent (this=0x9142dac, e=0xbfd89530) at kernel/qtimer.cpp:271
#15 0x0539ca94 in QObject::event (this=0x9142dac, e=0xbfd89530) at kernel/qobject.cpp:1212
#16 0x418b6d2c in QApplicationPrivate::notify_helper (this=0x8f88d60, receiver=0x9142dac, e=0xbfd89530) at kernel/qapplication.cpp:4300
#17 0x418bd556 in QApplication::notify (this=0xbfd898a8, receiver=0x9142dac, e=0xbfd89530) at kernel/qapplication.cpp:3704
#18 0x058da58b in KApplication::notify (this=0xbfd898a8, receiver=0x9142dac, event=0xbfd89530) at /usr/src/debug/kdelibs-4.4.0/kdeui/kernel/kapplication.cpp:302
#19 0x067a68a0 in KWin::Application::notify (this=0xbfd898a8, o=0x9142dac, e=0xbfd89530) at /usr/src/debug/kdebase-workspace-4.4.0/kwin/main.cpp:370
#20 0x0538cc03 in QCoreApplication::notifyInternal (this=0xbfd898a8, receiver=0x9142dac, event=0xbfd89530) at kernel/qcoreapplication.cpp:704
#21 0x053b7afe in sendEvent (this=0x8f8bf34) at kernel/qcoreapplication.h:215
#22 QTimerInfoList::activateTimers (this=0x8f8bf34) at kernel/qeventdispatcher_unix.cpp:603
#23 0x053b5188 in timerSourceDispatch (source=0x8f8bf68) at kernel/qeventdispatcher_glib.cpp:184
#24 idleTimerSourceDispatch (source=0x8f8bf68) at kernel/qeventdispatcher_glib.cpp:231
#25 0x0086af88 in g_main_dispatch (context=<value optimized out>) at gmain.c:1960
#26 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2513
#27 0x0086e8b8 in g_main_context_iterate (context=<value optimized out>, block=<value optimized out>, dispatch=<value optimized out>, self=<value optimized out>) at gmain.c:2591
#28 0x0086e9e4 in IA__g_main_context_iteration (context=0x8f8b090, may_block=<value optimized out>) at gmain.c:2654
#29 0x053b4e46 in QEventDispatcherGlib::processEvents (this=0x8f73a90, flags=...) at kernel/qeventdispatcher_glib.cpp:412
#30 0x419650c6 in QGuiEventDispatcherGlib::processEvents (this=0x8f73a90, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#31 0x0538b2da in QEventLoop::processEvents (this=0xbfd897f4, flags=...) at kernel/qeventloop.cpp:149
#32 0x0538b61a in QEventLoop::exec (this=0xbfd897f4, flags=...) at kernel/qeventloop.cpp:201
#33 0x0538dce7 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#34 0x418b6dd8 in QApplication::exec () at kernel/qapplication.cpp:3579
#35 0x067a8e47 in kdemain (argc=1, argv=0xbfd89aa4) at /usr/src/debug/kdebase-workspace-4.4.0/kwin/main.cpp:526
#36 0x0804872c in main (argc=1, argv=0xbfd89aa4) at /usr/src/debug/kdebase-workspace-4.4.0/i686-redhat-linux-gnu/kwin/kwin_dummy.cpp:3

Reported using DrKonqi