Version:            (using KDE 4.2.4)
OS:                Linux
Installed from:    Fedora RPMs

At random, when switching windows, kwin crashes with this trace:

Application: KWin (kwin), signal SIGSEGV
[Current thread is 1 (Thread 0xb80497a0 (LWP 2738))]

Thread 1 (Thread 0xb80497a0 (LWP 2738)):
[KCrash Handler]
#6  WindowPaintData (this=0xbfd71d60, w=0x0) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/lib/kwineffects.cpp:74
#7  0x009186cc in KWin::BoxSwitchEffect::paintWindowThumbnail (this=0x8f110e0, w=0x0) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects/boxswitch.cpp:761
#8  0x0091b9a2 in KWin::BoxSwitchEffect::paintScreen (this=0x8f110e0, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects/boxswitch.cpp:147
#9  0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#10 0x005a5af6 in KWin::Effect::paintScreen (this=0x8fc3778, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/lib/kwineffects.cpp:199
#11 0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#12 0x005a5af6 in KWin::Effect::paintScreen (this=0x8f1ff50, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/lib/kwineffects.cpp:199
#13 0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#14 0x005a5af6 in KWin::Effect::paintScreen (this=0x8f1c1d8, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/lib/kwineffects.cpp:199
#15 0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#16 0x00975aa0 in KWin::TrackMouseEffect::paintScreen (this=0x8eaf180, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects/trackmouse.cpp:71
#17 0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#18 0x00950d9d in KWin::ZoomEffect::paintScreen (this=0x8ec0700, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects/zoom.cpp:73
#19 0x0563afbf in KWin::EffectsHandlerImpl::paintScreen (this=0x8ec0070, mask=0, region={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}},
    data=@0xbfd722c8) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/effects.cpp:122
#20 0x05628570 in KWin::Scene::paintScreen (this=0x8fad640, mask=0xbfd723a4, region=0xbfd72464) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/scene.cpp:133
#21 0x05634f0a in KWin::SceneOpenGL::paint (this=0x8fad640, damage={d = 0x9722ac8, static shared_empty = {ref = {_q_value = 444}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}}, toplevels=
        {{p = {static shared_null = {ref = {_q_value = 4904}, alloc = 0, begin = 0, end = 0, sharable = 1, array = {0x0}}, d = 0x92c85c0}, d = 0x92c85c0}})
    at /usr/src/debug/kdebase-workspace-4.2.3/kwin/scene_opengl.cpp:724
#22 0x05623ed6 in KWin::Workspace::performCompositing (this=0x8df9160) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/composite.cpp:384
#23 0x055c47cd in KWin::Workspace::qt_metacall (this=0x8df9160, _c=QMetaObject::InvokeMetaMethod, _id=140, _a=0xbfd72538)
    at /usr/src/debug/kdebase-workspace-4.2.3/i386-redhat-linux-gnu/kwin/workspace.moc:446
#24 0x054c2a08 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#25 0x054c4192 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#26 0x054fe417 in QTimer::timeout () from /usr/lib/libQtCore.so.4
#27 0x054c845e in QTimer::timerEvent () from /usr/lib/libQtCore.so.4
#28 0x054bcebf in QObject::event () from /usr/lib/libQtCore.so.4
#29 0x024c9cec in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#30 0x024d1fce in QApplication::notify () from /usr/lib/libQtGui.so.4
#31 0x07b584fd in KApplication::notify () from /usr/lib/libkdeui.so.5
#32 0x055d92dd in KWin::Application::notify (this=0xbfd72cb4, o=0x8df93b4, e=0xbfd729dc) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/main.cpp:368
#33 0x054ac75b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#34 0x054dba41 in ?? () from /usr/lib/libQtCore.so.4
#35 0x054d8230 in ?? () from /usr/lib/libQtCore.so.4
#36 0x00147258 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#37 0x0014a903 in ?? () from /lib/libglib-2.0.so.0
#38 0x0014aac1 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#39 0x054d8188 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#40 0x02569665 in ?? () from /usr/lib/libQtGui.so.4
#41 0x054aad8a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#42 0x054ab1ca in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#43 0x054ad679 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#44 0x024c9b67 in QApplication::exec () from /usr/lib/libQtGui.so.4
#45 0x055dc32a in kdemain (argc=1, argv=0xbfd72e84) at /usr/src/debug/kdebase-workspace-4.2.3/kwin/main.cpp:519
#46 0x08048722 in main (argc=9988136, argv=0x762201) at /usr/src/debug/kdebase-workspace-4.2.3/i386-redhat-linux-gnu/kwin/kwin_dummy.cpp:3