Version:           4.3.5 (using KDE 4.3.5)
OS:                Linux
Installed from:    Ubuntu Packages

Hi,

I have a reproducable bug on a kde 3.5.7 with kwin in karmic kubuntu: When I am using the "cover switch" to switch between windows and one of the open windows disappears kwin seg faults. I can reproduce this when I use Thunderbird to send an email and start switching windows before the email was entirely sent. The editor-window in which the email was written closes itself once the email is sent, if this happens during switching it leads to kwin crashing.
I have desktop effects enabled and am using "minimise animation", "shadow", "slide", "translucency", "dialogue parent", "cover switch", "desktop grip" and "present windows"
I saw the following bug and hope that I'm not creating a duplicate: https://bugs.kde.org/show_bug.cgi?id=184602 describing
It is a very similar issue, but the bugreport is marked as solved and my kwin does not crash when I use alt+tab after opening the k-menu.

For some reason I could not send the report through the crash handler, I saved the report instead:
Application that crashed: kwin
Version of the application: 4.3.5 (KDE 4.3.5)
KDE Version: 4.3.5 (KDE 4.3.5)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-17-generic i686
Distribution: Ubuntu 9.10

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  0x0183403f in KWin::CoverSwitchEffect::calculateItemSizes (this=0x872dca0) at ../../../kwin/effects/coverswitch/coverswitch.cpp:1063
#7  0x018349cf in KWin::CoverSwitchEffect::tabBoxUpdated (this=0x872dca0) at ../../../kwin/effects/coverswitch/coverswitch.cpp:678
#8  0x00367ea3 in KWin::EffectsHandlerImpl::tabBoxUpdated (this=0x86990a0) at ../../kwin/effects.cpp:295
#9  0x002f9051 in KWin::TabBox::setCurrentClient (this=0x8792518, newClient=0x892d820) at ../../kwin/tabbox.cpp:538
#10 0x002f9217 in KWin::TabBox::nextPrev (this=0x8792518, next=true) at ../../kwin/tabbox.cpp:438
#11 0x002d7c25 in KWin::Workspace::removeClient (this=0x8663c98, c=0x8af6a38) at ../../kwin/workspace.cpp:627
#12 0x002e50da in KWin::Client::releaseWindow (this=0x8af6a38, on_shutdown=false) at ../../kwin/client.cpp:240
#13 0x0030738d in KWin::Client::unmapNotifyEvent (this=0x8af6a38, e=0xbfa0cbcc) at ../../kwin/events.cpp:796
#14 0x00308b04 in KWin::Client::windowEvent (this=0x8af6a38, e=0xbfa0cbcc) at ../../kwin/events.cpp:642
#15 0x003092c4 in KWin::Workspace::workspaceEvent (this=0x8663c98, e=0xbfa0cbcc) at ../../kwin/events.cpp:305
#16 0x002ef642 in KWin::Application::x11EventFilter (this=0xbfa0cf78, e=0xbfa0cbcc) at ../../kwin/main.cpp:357
#17 0x060d3d70 in qt_x11EventFilter (ev=0xbfa0cbcc) at kernel/qapplication_x11.cpp:375
#18 0x060e5375 in QApplication::x11ProcessEvent (this=0xbfa0cf78, event=0xbfa0cbcc) at kernel/qapplication_x11.cpp:3271
#19 0x06113502 in x11EventSourceDispatch (s=0x8450c00, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#20 0x016efe88 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#21 0x016f3730 in ?? () from /lib/libglib-2.0.so.0
#22 0x016f3863 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#23 0x0138902c in QEventDispatcherGlib::processEvents (this=0x8437b68, flags=...) at kernel/qeventdispatcher_glib.cpp:327
#24 0x06112be5 in QGuiEventDispatcherGlib::processEvents (this=0x8437b68, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#25 0x0135cc79 in QEventLoop::processEvents (this=0xbfa0cec4, flags=) at kernel/qeventloop.cpp:149
#26 0x0135d0ca in QEventLoop::exec (this=0xbfa0cec4, flags=...) at kernel/qeventloop.cpp:201
#27 0x0135f53f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#28 0x06071dd7 in QApplication::exec () at kernel/qapplication.cpp:3525
#29 0x002f21c4 in kdemain (argc=3, argv=0xbfa0d174) at ../../kwin/main.cpp:522
#30 0x080485cb in main (argc=3, argv=0xbfa0d174) at kwin_dummy.cpp:3

If you need any more information please let me know.