Application that crashed: kwin
Version of the application: 4.3.1 (KDE 4.3.1)
KDE Version: 4.3.1 (KDE 4.3.1)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-ARCH i686

What I was doing when the application crashed:
im using alt+tab and it crashed

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  0xb771d0ea in KWin::WindowPaintData::WindowPaintData () from /usr/lib/libkwineffects.so.1
#7  0xb1868fba in KWin::CoverSwitchEffect::paintWindows () from /usr/lib/kde4/kwin4_effect_builtins.so
#8  0xb186981b in KWin::CoverSwitchEffect::paintScene () from /usr/lib/kde4/kwin4_effect_builtins.so
#9  0xb186feab in KWin::CoverSwitchEffect::paintScreen () from /usr/lib/kde4/kwin4_effect_builtins.so
#10 0xb7f09160 in KWin::EffectsHandlerImpl::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#11 0xb771aab6 in KWin::Effect::paintScreen () from /usr/lib/libkwineffects.so.1
#12 0xb7f09160 in KWin::EffectsHandlerImpl::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#13 0xb771aab6 in KWin::Effect::paintScreen () from /usr/lib/libkwineffects.so.1
#14 0xb7f09160 in KWin::EffectsHandlerImpl::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#15 0xb18934e9 in KWin::TrackMouseEffect::paintScreen () from /usr/lib/kde4/kwin4_effect_builtins.so
#16 0xb7f09160 in KWin::EffectsHandlerImpl::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#17 0xb1866b20 in KWin::ZoomEffect::paintScreen () from /usr/lib/kde4/kwin4_effect_builtins.so
#18 0xb7f09160 in KWin::EffectsHandlerImpl::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#19 0xb7ef1d74 in KWin::Scene::paintScreen () from /usr/lib/libkdeinit4_kwin.so
#20 0xb7f01913 in KWin::SceneOpenGL::paint () from /usr/lib/libkdeinit4_kwin.so
#21 0xb7eed461 in KWin::Workspace::performCompositing () from /usr/lib/libkdeinit4_kwin.so
#22 0xb7e7c5ca in KWin::Workspace::qt_metacall () from /usr/lib/libkdeinit4_kwin.so
#23 0xb67ec26c in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#24 0xb67ecea2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#25 0xb6826347 in QTimer::timeout () from /usr/lib/libQtCore.so.4
#26 0xb67f191e in QTimer::timerEvent () from /usr/lib/libQtCore.so.4
#27 0xb67e641f in QObject::event () from /usr/lib/libQtCore.so.4
#28 0xb6a463e4 in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#29 0xb6a4dacc in QApplication::notify () from /usr/lib/libQtGui.so.4
#30 0xb7b5543a in KApplication::notify () from /usr/lib/libkdeui.so.5
#31 0xb7e9212f in KWin::Application::notify () from /usr/lib/libkdeinit4_kwin.so
#32 0xb67d688b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#33 0xb680405e in ?? () from /usr/lib/libQtCore.so.4
#34 0xb6801040 in ?? () from /usr/lib/libQtCore.so.4
#35 0xb3f70d98 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#36 0xb3f743e0 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#37 0xb3f74513 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#38 0xb6800f8c in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#39 0xb6ae4115 in ?? () from /usr/lib/libQtGui.so.4
#40 0xb67d4e39 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#41 0xb67d528a in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#42 0xb67d76ff in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#43 0xb6a46267 in QApplication::exec () from /usr/lib/libQtGui.so.4
#44 0xb7e94a94 in kdemain () from /usr/lib/libkdeinit4_kwin.so
#45 0x0804857b in _start ()

Reported using DrKonqi