Application that crashed: kwin
Version of the application: 4.3.2 (KDE 4.3.2)
KDE Version: 4.3.2 (KDE 4.3.2)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-19-generic-pae i686
Distribution: Ubuntu 9.10

What I was doing when the application crashed:
I was closing all applications on my Dell Latitude E6400 when kwin crashed while thunderbird was closing. I used ALT+TAB to switch around and check if there was any other open applications less than a second before the crash.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  WindowPaintData (this=0xbfdc7880, w=0x1) at ../../../kwin/lib/kwineffects.cpp:76
#7  0xb1780917 in KWin::CoverSwitchEffect::paintFrontWindow (this=0x866a3c8, frontWindow=0x1, width=1440, leftWindows=0, rightWindows=0, reflectedWindow=false)
    at ../../../kwin/effects/coverswitch/coverswitch.cpp:801
#8  0xb1781c28 in KWin::CoverSwitchEffect::paintScene (this=0x866a3c8, frontWindow=0x1, leftWindows=..., rightWindows=..., reflectedWindows=false)
    at ../../../kwin/effects/coverswitch/coverswitch.cpp:436
#9  0xb17881f3 in KWin::CoverSwitchEffect::paintScreen (this=0x866a3c8, mask=32, region=..., data=...) at ../../../kwin/effects/coverswitch/coverswitch.cpp:308
#10 0xb7762a90 in KWin::EffectsHandlerImpl::paintScreen (this=0x8561038, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#11 0xb6f8bc66 in KWin::Effect::paintScreen (this=0x867c898, mask=32, region=..., data=...) at ../../../kwin/lib/kwineffects.cpp:206
#12 0xb7762a90 in KWin::EffectsHandlerImpl::paintScreen (this=0x8561038, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#13 0xb177edd3 in KWin::ZoomEffect::paintScreen (this=0x8562168, mask=32, region=..., data=...) at ../../../kwin/effects/zoom/zoom.cpp:73
#14 0xb7762a90 in KWin::EffectsHandlerImpl::paintScreen (this=0x8561038, mask=32, region=..., data=...) at ../../kwin/effects.cpp:122
#15 0xb774b604 in KWin::Scene::paintScreen (this=0x8506220, mask=0xbfdc7dc8, region=0xbfdc7e88) at ../../kwin/scene.cpp:134
#16 0xb775b213 in KWin::SceneOpenGL::paint (this=0x8506220, damage=..., toplevels=...) at ../../kwin/scene_opengl.cpp:746
#17 0xb7746cd1 in KWin::Workspace::performCompositing (this=0x8561498) at ../../kwin/composite.cpp:420
#18 0xb76d579a in KWin::Workspace::qt_metacall (this=0x8561498, _c=QMetaObject::InvokeMetaMethod, _id=153, _a=0xbfdc7f7c) at ./workspace.moc:473
#19 0xb6018263 in QMetaObject::activate (sender=0x85616fc, from_signal_index=4, to_signal_index=4, argv=0x0) at kernel/qobject.cpp:3113
#20 0xb6018ec2 in QMetaObject::activate (sender=0x85616fc, m=0xb60f3904, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3187
#21 0xb6052667 in QTimer::timeout (this=0x85616fc) at .moc/release-shared/moc_qtimer.cpp:128
#22 0xb601d9ae in QTimer::timerEvent (this=0x85616fc, e=0xbfdc8430) at kernel/qtimer.cpp:261
#23 0xb60123bf in QObject::event (this=0x85616fc, e=0xbfdc8430) at kernel/qobject.cpp:1075
#24 0xb6289f54 in QApplicationPrivate::notify_helper (this=0x8441db0, receiver=0x85616fc, e=0xbfdc8430) at kernel/qapplication.cpp:4056
#25 0xb629167c in QApplication::notify (this=0xbfdc87a8, receiver=0x85616fc, e=0xbfdc8430) at kernel/qapplication.cpp:3603
#26 0xb73acbfa in KApplication::notify (this=0xbfdc87a8, receiver=0x85616fc, event=0xbfdc8430) at ../../kdeui/kernel/kapplication.cpp:302
#27 0xb76eb46f in KWin::Application::notify (this=0xbfdc87a8, o=0x85616fc, e=0xbfdc8430) at ../../kwin/main.cpp:366
#28 0xb60026cb in QCoreApplication::notifyInternal (this=0xbfdc87a8, receiver=0x85616fc, event=0xbfdc8430) at kernel/qcoreapplication.cpp:610
#29 0xb602f7ce in QCoreApplication::sendEvent (this=0x8444d84) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#30 QTimerInfoList::activateTimers (this=0x8444d84) at kernel/qeventdispatcher_unix.cpp:572
#31 0xb602d0e0 in timerSourceDispatch (source=0x8444d50) at kernel/qeventdispatcher_glib.cpp:165
#32 0xb3766e88 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#33 0xb376a730 in ?? () from /lib/libglib-2.0.so.0
#34 0xb376a863 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#35 0xb602d02c in QEventDispatcherGlib::processEvents (this=0x8415b68, flags=...) at kernel/qeventdispatcher_glib.cpp:327
#36 0xb632abe5 in QGuiEventDispatcherGlib::processEvents (this=0x8415b68, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#37 0xb6000c79 in QEventLoop::processEvents (this=0xbfdc86f4, flags=) at kernel/qeventloop.cpp:149
#38 0xb60010ca in QEventLoop::exec (this=0xbfdc86f4, flags=...) at kernel/qeventloop.cpp:201
#39 0xb600353f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#40 0xb6289dd7 in QApplication::exec () at kernel/qapplication.cpp:3525
#41 0xb76ee034 in kdemain (argc=3, argv=0xbfdc89a4) at ../../kwin/main.cpp:522
#42 0x080485cb in main (argc=3, argv=0xbfdc89a4) at kwin_dummy.cpp:3

Reported using DrKonqi