Version:            (using KDE 4.0.0)
Installed from:    Ubuntu Packages

I just had kwin crashing while closing and restarting Amarok. After closing Amarok then ("minimize to tray"), kwin crashed.

I could not reproduce it and I'm not sure it's related to Amarok really.. it just happens to be the last thing I've been doing.

Backtrace:
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0xb5daf6e0 (LWP 25529)]
[New Thread 0xaef33b90 (LWP 28320)]
[KCrash handler]
#6  WindowPaintData (this=0xbfbd3a10, w=0x0)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/lib/kwineffects.cpp:69
#7  0xb3956202 in KWin::TaskbarThumbnailEffect::paintWindow (this=0x81e7b40, 
    w=0x824a6f8, mask=2, region=@0xbfbd3af8, data=@0xbfbd3b38)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/taskbarthumbnail.cpp:73
#8  0xb7f6aa82 in KWin::EffectsHandlerImpl::paintWindow (this=0x8142638, 
    w=0x824a6f8, mask=2, region=@0xbfbd3b90, data=@0xbfbd3b38)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:144
#9  0xb7f58ba9 in KWin::Scene::paintWindow (this=0x81abca8, w=0x8540fb8, 
    mask=2, region=@0xbfbd3d50, quads=@0xbfbd3d4c)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/scene.cpp:293
#10 0xb7f598dd in KWin::Scene::paintSimpleScreen (this=0x81abca8, 
    orig_mask=<value optimized out>, region=@0xbfbd3dd8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/scene.cpp:280
#11 0xb7f585bb in KWin::Scene::finalPaintScreen (this=0x81abca8, 
    mask=<value optimized out>, region=@0xbfbd3e14, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/scene.cpp:171
#12 0xb7f6abbb in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd3e58, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:117
#13 0xb3962404 in KWin::ShadowEffect::paintScreen (this=0x81dea38, mask=0, 
    region=@0xbfbd3e98, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/shadow.cpp:60
#14 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd3f04, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#15 0xb3951c70 in KWin::PresentWindowsEffect::paintScreen (this=0x81e79c8, 
    mask=0, region=@0xbfbd3f48, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/presentwindows.cpp:139
#16 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd3f88, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#17 0xb6ef1016 in KWin::Effect::paintScreen (this=0x812b980, mask=0, 
    region=@0xbfbd3fc8, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/lib/kwineffects.cpp:178
#18 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4058, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#19 0xb393fe29 in KWin::BoxSwitchEffect::paintScreen (this=0x81e82d8, mask=0, 
    region=@0xbfbd4098, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/boxswitch.cpp:92
#20 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4108, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#21 0xb3945db2 in KWin::DesktopGridEffect::paintScreen (this=0x81e6c40, 
    mask=0, region=@0xbfbd4148, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/desktopgrid.cpp:123
#22 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4188, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#23 0xb6ef1016 in KWin::Effect::paintScreen (this=0x81ee4d0, mask=0, 
    region=@0xbfbd41c8, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/lib/kwineffects.cpp:178
#24 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4208, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#25 0xb6ef1016 in KWin::Effect::paintScreen (this=0x81a8390, mask=0, 
    region=@0xbfbd4248, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/lib/kwineffects.cpp:178
#26 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4304, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#27 0xb3957bdf in KWin::ThumbnailAsideEffect::paintScreen (this=0x81ea220, 
    mask=0, region=@0xbfbd4348, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/thumbnailaside.cpp:52
#28 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4394, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#29 0xb395945d in KWin::ZoomEffect::paintScreen (this=0x81db180, mask=0, 
    region=@0xbfbd43d8, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects/zoom.cpp:72
#30 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd4418, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#31 0xb6ef1016 in KWin::Effect::paintScreen (this=0x81e7b40, mask=0, 
    region=@0xbfbd4458, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/lib/kwineffects.cpp:178
#32 0xb7f6ab6b in KWin::EffectsHandlerImpl::paintScreen (this=0x8142638, 
    mask=0, region=@0xbfbd44e0, data=@0xbfbd44a8)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/effects.cpp:113
#33 0xb7f59b73 in KWin::Scene::paintScreen (this=0x81abca8, mask=0xbfbd455c, 
    region=0xbfbd4674)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/scene.cpp:131
#34 0xb7f62ba5 in KWin::SceneOpenGL::paint (this=0x81abca8, 
    damage=@0xbfbd4674, toplevels=@0xbfbd4670)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/scene_opengl.cpp:587
#35 0xb7f540f8 in KWin::Workspace::performCompositing (this=0x8128720)
    at /build/buildd/kdebase-workspace-4.0.0/kwin/composite.cpp:325
#36 0xb7ef6762 in KWin::Workspace::qt_metacall (this=0x8128720, 
    _c=QMetaObject::InvokeMetaMethod, _id=135, _a=0xbfbd4770)
    at /build/buildd/kdebase-workspace-4.0.0/obj-i486-linux-gnu/kwin/workspace.moc:427
#37 0xb7cfdcb4 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#38 0xb7cfe882 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#39 0xb7d1c127 in QTimer::timeout () from /usr/lib/libQtCore.so.4
#40 0xb7d0484e in QTimer::timerEvent () from /usr/lib/libQtCore.so.4
#41 0xb7cfc874 in QObject::event () from /usr/lib/libQtCore.so.4
#42 0xb73142ad in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#43 0xb7317d07 in QApplication::notify () from /usr/lib/libQtGui.so.4
#44 0xb70a1f93 in KApplication::notify (this=0xbfbd5324, receiver=0x812896c, 
    event=0xbfbd5068)
    at /build/buildd/kde4libs-4.0.0/kdeui/kernel/kapplication.cpp:314
#45 0xb7f109ca in KWin::Application::notify (this=0xbfbd5324, o=0x812896c, 
    e=0xbfbd5068) at /build/buildd/kdebase-workspace-4.0.0/kwin/main.cpp:287
#46 0xb7ceaccb in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#47 0xb7d11e49 in ?? () from /usr/lib/libQtCore.so.4
#48 0xbfbd5324 in ?? ()
#49 0x0812896c in ?? ()
#50 0xbfbd5068 in ?? ()
#51 0xb7cec77d in QCoreApplication::sendPostedEvents ()
   from /usr/lib/libQtCore.so.4
#52 0xb7d0e960 in ?? () from /usr/lib/libQtCore.so.4
#53 0x0805d774 in ?? ()
#54 0xb6c97248 in ?? () from /usr/lib/libglib-2.0.so.0
#55 0xbfbd50f8 in ?? ()
#56 0xb6c20d76 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
Backtrace stopped: frame did not save the PC
#0  0xb7f80410 in __kernel_vsyscall ()