Application that crashed: kwin
Version of the application: 4.2.96 (KDE 4.2.96 (KDE 4.3 RC2))
KDE Version: 4.2.96 (KDE 4.2.96 (KDE 4.3 RC2))
Qt Version: 4.5.2
Operating System: Linux 2.6.30-1-686 i686
Distribution: Debian GNU/Linux unstable (sid)

What I was doing when the application crashed:
I dod not know how to reproduce it

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  0xb1ec94bf in KWin::BoxSwitchEffect::calculateItemSizes (this=0x8ecf1c8) at ../../../kwin/effects/boxswitch/boxswitch.cpp:686
#7  0xb1ecadb5 in KWin::BoxSwitchEffect::tabBoxUpdated (this=0x8ecf1c8) at ../../../kwin/effects/boxswitch/boxswitch.cpp:428
#8  0xb7ebb19b in KWin::EffectsHandlerImpl::tabBoxUpdated (this=0x8db51a0) at ../../kwin/effects.cpp:293
#9  0xb7e4ed33 in KWin::TabBox::setCurrentClient (this=0x8fcb730, newClient=0x9176140) at ../../kwin/tabbox.cpp:538
#10 0xb7e4f322 in KWin::TabBox::nextPrev (this=0x8fcb730, next=true) at ../../kwin/tabbox.cpp:438
#11 0xb7e2fb75 in KWin::Workspace::removeClient (this=0x8db63f8, c=0x9bae730) at ../../kwin/workspace.cpp:627
#12 0xb7e3c4da in KWin::Client::releaseWindow (this=0x9bae730, on_shutdown=false) at ../../kwin/client.cpp:235
#13 0xb7e5f07b in KWin::Client::unmapNotifyEvent (this=0x9bae730, e=0xbfc65a3c) at ../../kwin/events.cpp:796
#14 0xb7e609e7 in KWin::Client::windowEvent (this=0x9bae730, e=0xbfc65a3c) at ../../kwin/events.cpp:642
#15 0xb7e60e1c in KWin::Workspace::workspaceEvent (this=0x8db63f8, e=0xbfc65a3c) at ../../kwin/events.cpp:319
#16 0xb7e47f82 in KWin::Application::x11EventFilter (this=0xbfc65d54, e=0xbfc65a3c) at ../../kwin/main.cpp:362
#17 0xb6a77a8e in qt_x11EventFilter (ev=0xbfc65a3c) at kernel/qapplication_x11.cpp:375
#18 0xb6a89b2b in QApplication::x11ProcessEvent (this=0xbfc65d54, event=0xbfc65a3c) at kernel/qapplication_x11.cpp:3271
#19 0xb6ab5842 in x11EventSourceDispatch (s=0x8c886a8, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#20 0xb3f66368 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#21 0xb3f698c3 in ?? () from /usr/lib/libglib-2.0.so.0
#22 0xb3f69a48 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#23 0xb67947f8 in QEventDispatcherGlib::processEvents (this=0x8c595b0, flags=...) at kernel/qeventdispatcher_glib.cpp:327
#24 0xb6ab4f85 in QGuiEventDispatcherGlib::processEvents (this=0x8c595b0, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#25 0xb6767fba in QEventLoop::processEvents (this=0xbfc65ca0, flags=...) at kernel/qeventloop.cpp:149
#26 0xb6768402 in QEventLoop::exec (this=0xbfc65ca0, flags=...) at kernel/qeventloop.cpp:201
#27 0xb676a859 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#28 0xb6a15657 in QApplication::exec () at kernel/qapplication.cpp:3525
#29 0xb7e4a5cf in kdemain (argc=1, argv=0xbfc65f34) at ../../kwin/main.cpp:527
#30 0x08048582 in main (argc=157998552, argv=0x968cd30) at kwin_dummy.cpp:3

Reported using DrKonqi