Version:            (using KDE 4.3.0)
Compiler:          gcc version 4.3.4 (Gentoo 4.3.4 p1.0, pie-10.1.5) Target: x86_64-pc-linux-gnu
OS:                Linux
Installed from:    Gentoo Packages

I switch windows using the Cover Switch effect. Sometimes when I choose the right window and release the alt key, the screen zooms half way to the selected window, halts for a fraction of second and then kwin crashes and restarts itself. Unfortunately I am unable to reproduce it on a regular basis.

I am using nvidia proprietary drivers (185.18.31).

The backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#5  0x00007f5e85c54554 in KWin::CoverSwitchEffect::calculateItemSizes () from /usr/lib64/kde4/kwin4_effect_builtins.so
#6  0x00007f5e85c5582b in KWin::CoverSwitchEffect::prePaintScreen () from /usr/lib64/kde4/kwin4_effect_builtins.so
#7  0x00000036016a907a in KWin::EffectsHandlerImpl::prePaintScreen () from /usr/lib64/libkdeinit4_kwin.so
#8  0x00000036016a907a in KWin::EffectsHandlerImpl::prePaintScreen () from /usr/lib64/libkdeinit4_kwin.so
#9  0x00007f5e85c2601c in KWin::LoginEffect::prePaintScreen () from /usr/lib64/kde4/kwin4_effect_builtins.so
#10 0x00000036016a907a in KWin::EffectsHandlerImpl::prePaintScreen () from /usr/lib64/libkdeinit4_kwin.so
#11 0x00007f5e85c78ffa in KWin::TrackMouseEffect::prePaintScreen () from /usr/lib64/kde4/kwin4_effect_builtins.so
#12 0x00000036016a907a in KWin::EffectsHandlerImpl::prePaintScreen () from /usr/lib64/libkdeinit4_kwin.so
#13 0x00000036016a907a in KWin::EffectsHandlerImpl::prePaintScreen () from /usr/lib64/libkdeinit4_kwin.so
#14 0x0000003601694ace in KWin::Scene::paintScreen () from /usr/lib64/libkdeinit4_kwin.so
#15 0x00000036016a35a7 in KWin::SceneOpenGL::paint () from /usr/lib64/libkdeinit4_kwin.so
#16 0x0000003601690034 in KWin::Workspace::performCompositing () from /usr/lib64/libkdeinit4_kwin.so
#17 0x000000360162cc0a in KWin::Workspace::qt_metacall () from /usr/lib64/libkdeinit4_kwin.so
#18 0x0000003600d41f8d in QMetaObject::activate () from /usr/lib64/qt4/libQtCore.so.4
#19 0x0000003600d3e823 in QObject::event () from /usr/lib64/qt4/libQtCore.so.4
#20 0x0000003601b9cc8d in QApplicationPrivate::notify_helper () from /usr/lib64/qt4/libQtGui.so.4
#21 0x0000003601ba46ba in QApplication::notify () from /usr/lib64/qt4/libQtGui.so.4
#22 0x0000003604c1c5cb in KApplication::notify () from /usr/lib64/libkdeui.so.5
#23 0x0000003600d2fe8b in QCoreApplication::notifyInternal () from /usr/lib64/qt4/libQtCore.so.4
#24 0x0000003600d5819e in QTimerInfoList::activateTimers () from /usr/lib64/qt4/libQtCore.so.4
#25 0x0000003600d550cd in timerSourceDispatch () from /usr/lib64/qt4/libQtCore.so.4
#26 0x00000035fd439dc9 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#27 0x00000035fd43d518 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#28 0x00000035fd43d6dc in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#29 0x0000003600d5502f in QEventDispatcherGlib::processEvents () from /usr/lib64/qt4/libQtCore.so.4
#30 0x0000003601c2312f in QGuiEventDispatcherGlib::processEvents () from /usr/lib64/qt4/libQtGui.so.4
#31 0x0000003600d2e832 in QEventLoop::processEvents () from /usr/lib64/qt4/libQtCore.so.4
#32 0x0000003600d2e9cc in QEventLoop::exec () from /usr/lib64/qt4/libQtCore.so.4
#33 0x0000003600d30a6c in QCoreApplication::exec () from /usr/lib64/qt4/libQtCore.so.4
#34 0x00000036016448d5 in kdemain () from /usr/lib64/libkdeinit4_kwin.so
#35 0x00000035f9c1e5c6 in __libc_start_main () from /lib/libc.so.6
#36 0x0000000000400789 in _start ()