Application that crashed: kwin
Version of the application: 4.3.2 (KDE 4.3.2)
KDE Version: 4.3.2 (KDE 4.3.2)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-16-generic x86_64
Distribution: Ubuntu 9.10

What I was doing when the application crashed:
I have seen kwin crash when changing settings from within Kubuntu's "System settings" panel, this is just an example. This happens relatively rarely.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
The current source language is "auto; currently c".
[KCrash Handler]
#5  QBasicAtomicInt::ref (this=0x19450b0, desktop=4, areas=) at /usr/include/qt4/QtCore/qatomic_x86_64.h:121
#6  QVector (this=0x19450b0, desktop=4, areas=) at /usr/include/qt4/QtCore/qvector.h:113
#7  QForeachContainer (this=0x19450b0, desktop=4, areas=) at /usr/include/qt4/QtCore/qglobal.h:2054
#8  KWin::Workspace::previousRestrictedMoveArea (this=0x19450b0, desktop=4, areas=) at ../../kwin/geometry.cpp:327
#9  0x00007f72cefacbed in KWin::Client::checkWorkspacePosition (this=0x271f100) at ../../kwin/geometry.cpp:1134
#10 0x00007f72cef649d4 in KWin::Client::updateDecoration (this=0x271f100, check_workspace_pos=true, force=<value optimized out>) at ../../kwin/client.cpp:352
#11 0x00007f72cef59657 in KWin::Workspace::slotReconfigure (this=0x19450b0) at ../../kwin/workspace.cpp:1055
#12 0x00007f72cef5a60c in KWin::Workspace::qt_metacall (this=0x19450b0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffa8bd0380) at ./workspace.moc:443
#13 0x00007f72cb1e2ddc in QMetaObject::activate (sender=0x1945368, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x7fffa8bd0180) at kernel/qobject.cpp:3113
#14 0x00007f72cb1dcd83 in QObject::event (this=0x1945368, e=0x19450b0) at kernel/qobject.cpp:1075
#15 0x00007f72cb8d1efc in QApplicationPrivate::notify_helper (this=0x1746e20, receiver=0x1945368, e=0x7fffa8bd0980) at kernel/qapplication.cpp:4056
#16 0x00007f72cb8d91ce in QApplication::notify (this=0x7fffa8bd0ce0, receiver=0x1945368, e=0x7fffa8bd0980) at kernel/qapplication.cpp:4021
#17 0x00007f72ce7c0ab6 in KApplication::notify (this=0x7fffa8bd0ce0, receiver=0x1945368, event=0x7fffa8bd0980) at ../../kdeui/kernel/kapplication.cpp:302
#18 0x00007f72cb1cdc2c in QCoreApplication::notifyInternal (this=0x7fffa8bd0ce0, receiver=0x1945368, event=0x7fffa8bd0980) at kernel/qcoreapplication.cpp:610
#19 0x00007f72cb1f8862 in QCoreApplication::sendEvent (this=0x174ab60) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#20 QTimerInfoList::activateTimers (this=0x174ab60) at kernel/qeventdispatcher_unix.cpp:572
#21 0x00007f72cb1f625d in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:165
#22 0x00007f72c4b80bce in g_main_dispatch (context=0x1749920) at /build/buildd/glib2.0-2.22.3/glib/gmain.c:1960
#23 IA__g_main_context_dispatch (context=0x1749920) at /build/buildd/glib2.0-2.22.3/glib/gmain.c:2513
#24 0x00007f72c4b84598 in g_main_context_iterate (context=0x1749920, block=<value optimized out>, dispatch=<value optimized out>, self=<value optimized out>)
    at /build/buildd/glib2.0-2.22.3/glib/gmain.c:2591
#25 0x00007f72c4b846c0 in IA__g_main_context_iteration (context=0x1749920, may_block=1) at /build/buildd/glib2.0-2.22.3/glib/gmain.c:2654
#26 0x00007f72cb1f61a6 in QEventDispatcherGlib::processEvents (this=0x172ce90, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#27 0x00007f72cb9664be in QGuiEventDispatcherGlib::processEvents (this=0x7fffa8bd00e0, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#28 0x00007f72cb1cc532 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#29 0x00007f72cb1cc904 in QEventLoop::exec (this=0x7fffa8bd0c20, flags=) at kernel/qeventloop.cpp:201
#30 0x00007f72cb1ceab9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#31 0x00007f72cef71094 in kdemain (argc=<value optimized out>, argv=<value optimized out>) at ../../kwin/main.cpp:522
#32 0x00007f72cebdbabd in __libc_start_main (main=<value optimized out>, argc=<value optimized out>, ubp_av=<value optimized out>, init=<value optimized out>, fini=<value optimized out>, 
    rtld_fini=<value optimized out>, stack_end=0x7fffa8bd11c8) at libc-start.c:220
#33 0x0000000000400679 in _start () at ../sysdeps/x86_64/elf/start.S:113

Reported using DrKonqi