Application: kwin (4.4.2 (KDE 4.4.2))
KDE Platform Version: 4.4.2 (KDE 4.4.2)
Qt Version: 4.6.2
Operating System: Linux 2.6.31-21-generic i686
Distribution: Ubuntu 10.04.1 LTS

-- Information about the crash:
The KWin crashed while swithing windows using the key combination 'Alt+Tab'. Other settings and actions during the time of crash: Cover Flow desktop effect activated for window switching. Firefox window (3) was closing itself while I attempted to switch between them.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[Current thread is 1 (Thread 0xb77ac720 (LWP 3465))]

Thread 2 (Thread 0xab823b70 (LWP 3466)):
#0  0x001eab71 in pthread_mutex_lock () from /lib/tls/i686/cmov/libc.so.6
#1  0x0134fb03 in IA__g_main_context_prepare (context=0xaaf004d8, priority=0xab82313c) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2282
#2  0x0134fee9 in g_main_context_iterate (context=0xaaf004d8, block=<value optimized out>, dispatch=1, self=0xaaf01ca0) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2571
#3  0x013504b8 in IA__g_main_context_iteration (context=0xaaf004d8, may_block=1) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2654
#4  0x087d760f in QEventDispatcherGlib::processEvents (this=0x8e1e978, flags=...) at kernel/qeventdispatcher_glib.cpp:414
#5  0x087aa059 in QEventLoop::processEvents (this=0xab823280, flags=) at kernel/qeventloop.cpp:149
#6  0x087aa4aa in QEventLoop::exec (this=0xab823280, flags=...) at kernel/qeventloop.cpp:201
#7  0x086a65a8 in QThread::exec (this=0x8f56588) at thread/qthread.cpp:487
#8  0x08789c1b in QInotifyFileSystemWatcherEngine::run (this=0x8f56588) at io/qfilesystemwatcher_inotify.cpp:248
#9  0x086a932e in QThreadPrivate::start (arg=0x8f56588) at thread/qthread_unix.cpp:248
#10 0x0075196e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#11 0x001dda4e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb77ac720 (LWP 3465)):
[KCrash Handler]
#6  QBasicAtomicInt::ref (this=0xbfd81f28, w=0x8cff668) at /usr/include/qt4/QtCore/qatomic_i386.h:120
#7  QList<KWin::WindowQuad>::operator= (this=0xbfd81f28, w=0x8cff668) at /usr/include/qt4/QtCore/qlist.h:411
#8  operator= (this=0xbfd81f28, w=0x8cff668) at ../../../kwin/lib/kwineffects.h:1066
#9  WindowPaintData (this=0xbfd81f28, w=0x8cff668) at ../../../kwin/lib/kwineffects.cpp:78
#10 0x05e35bdc in KWin::CoverSwitchEffect::paintWindows (this=0x8da57c0, windows=..., left=false, reflectedWindows=true, additionalWindow=0x8cff668)
    at ../../../kwin/effects/coverswitch/coverswitch.cpp:858
#11 0x05e36859 in KWin::CoverSwitchEffect::paintScene (this=0x8da57c0, frontWindow=0x8cff668, leftWindows=..., rightWindows=..., reflectedWindows=true)
    at ../../../kwin/effects/coverswitch/coverswitch.cpp:471
#12 0x05e37779 in KWin::CoverSwitchEffect::paintScreen (this=0x8da57c0, mask=32, region=..., data=...) at ../../../kwin/effects/coverswitch/coverswitch.cpp:252
#13 0x00c3cd30 in KWin::EffectsHandlerImpl::paintScreen (this=0x8d22db0, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#14 0x007dc426 in KWin::Effect::paintScreen (this=0x8da6df0, mask=32, region=..., data=...) at ../../../kwin/lib/kwineffects.cpp:227
#15 0x00c3cd30 in KWin::EffectsHandlerImpl::paintScreen (this=0x8d22db0, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#16 0x007dc426 in KWin::Effect::paintScreen (this=0x8db4200, mask=32, region=..., data=...) at ../../../kwin/lib/kwineffects.cpp:227
#17 0x00c3cd30 in KWin::EffectsHandlerImpl::paintScreen (this=0x8d22db0, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#18 0x00c24ca4 in KWin::Scene::paintScreen (this=0x8d292d0, mask=0xbfd824b8, region=0xbfd82584) at ../../kwin/scene.cpp:134
#19 0x00c3653a in KWin::SceneOpenGL::paint (this=0x8d292d0, damage=..., toplevels=...) at ../../kwin/scene_opengl.cpp:748
#20 0x00c1f604 in KWin::Workspace::performCompositing (this=0x8d0fca0) at ../../kwin/composite.cpp:424
#21 0x00b974a6 in KWin::Workspace::qt_metacall (this=0x8d0fca0, _c=QMetaObject::InvokeMetaMethod, _id=173, _a=0xbfd826ac) at ./workspace.moc:535
#22 0x087b0c9a in QMetaObject::metacall (object=0x8d0fca0, cl=6893556, idx=173, argv=0xbfd826ac) at kernel/qmetaobject.cpp:237
#23 0x087bf3d5 in QMetaObject::activate (sender=0x8d0ff28, m=0x88bf5a4, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3293
#24 0x08810aa7 in QTimer::timeout (this=0x8d0ff28) at .moc/release-shared/moc_qtimer.cpp:134
#25 0x087c760e in QTimer::timerEvent (this=0x8d0ff28, e=0xbfd82c00) at kernel/qtimer.cpp:271
#26 0x087bc254 in QObject::event (this=0x8d0ff28, e=0x7db634) at kernel/qobject.cpp:1212
#27 0x0210e4dc in QApplicationPrivate::notify_helper (this=0x8bf2488, receiver=0x8d0ff28, e=0xbfd82c00) at kernel/qapplication.cpp:4300
#28 0x0211505e in QApplication::notify (this=0xbfd82f78, receiver=0x8d0ff28, e=0xbfd82c00) at kernel/qapplication.cpp:3704
#29 0x00449f2a in KApplication::notify (this=0xbfd82f78, receiver=0x8d0ff28, event=0xbfd82c00) at ../../kdeui/kernel/kapplication.cpp:302
#30 0x00bb3def in KWin::Application::notify (this=0xbfd82f78, o=0x8d0ff28, e=0xbfd82c00) at ../../kwin/main.cpp:370
#31 0x087aba3b in QCoreApplication::notifyInternal (this=0xbfd82f78, receiver=0x8d0ff28, event=0xbfd82c00) at kernel/qcoreapplication.cpp:704
#32 0x087dad66 in QCoreApplication::sendEvent (this=0x8bf52a4) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#33 QTimerInfoList::activateTimers (this=0x8bf52a4) at kernel/qeventdispatcher_unix.cpp:603
#34 0x087d7917 in timerSourceDispatch (source=0x8bf5700) at kernel/qeventdispatcher_glib.cpp:184
#35 idleTimerSourceDispatch (source=0x8bf5700) at kernel/qeventdispatcher_glib.cpp:231
#36 0x0134c5e5 in g_main_dispatch (context=0x8bf4890) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:1960
#37 IA__g_main_context_dispatch (context=0x8bf4890) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2513
#38 0x013502d8 in g_main_context_iterate (context=0x8bf4890, block=<value optimized out>, dispatch=1, self=0x8bf2730) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2591
#39 0x013504b8 in IA__g_main_context_iteration (context=0x8bf4890, may_block=1) at /build/buildd/glib2.0-2.24.1/glib/gmain.c:2654
#40 0x087d75d5 in QEventDispatcherGlib::processEvents (this=0x8bdcde8, flags=...) at kernel/qeventdispatcher_glib.cpp:412
#41 0x021ce135 in QGuiEventDispatcherGlib::processEvents (this=0x8bdcde8, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#42 0x087aa059 in QEventLoop::processEvents (this=0xbfd82ec4, flags=) at kernel/qeventloop.cpp:149
#43 0x087aa4aa in QEventLoop::exec (this=0xbfd82ec4, flags=...) at kernel/qeventloop.cpp:201
#44 0x087ae69f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#45 0x0210e577 in QApplication::exec () at kernel/qapplication.cpp:3579
#46 0x00bb5a00 in kdemain (argc=1, argv=0xbfd83184) at ../../kwin/main.cpp:526
#47 0x0804860b in main (argc=1, argv=0xbfd83184) at kwin_dummy.cpp:3

Reported using DrKonqi