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 2.6.31-15-generic x86_64
Distribution: Ubuntu 9.10

What I was doing when the application crashed:
I was playing a video in windowed mode and tried going into full screen, or the other way around. I am not really sure which, because the windows were taking a long time to redraw and I might have issued multiple commands to alternate between the two modes.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#5  QWidget::internalWinId (this=0xf12100) at ../../include/QtGui/../../src/gui/kernel/qwidget.h:234
#6  QWidget::effectiveWinId (this=0xf12100) at kernel/qwidget.cpp:2223
#7  0x00007fb75c62e5f5 in QETWidget::translateMouseEvent (this=0xf12100, event=0x7fff014f4e80) at kernel/qapplication_x11.cpp:4291
#8  0x00007fb75c62daa9 in QApplication::x11ProcessEvent (this=<value optimized out>, event=0x7fff014f4e80) at kernel/qapplication_x11.cpp:3550
#9  0x00007fb75c656d0c in x11EventSourceDispatch (s=<value optimized out>, callback=<value optimized out>, user_data=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:146
#10 0x00007fb755870bbe in g_main_dispatch (context=0x888d20) at /build/buildd/glib2.0-2.22.2/glib/gmain.c:1960
#11 IA__g_main_context_dispatch (context=0x888d20) at /build/buildd/glib2.0-2.22.2/glib/gmain.c:2513
#12 0x00007fb755874588 in g_main_context_iterate (context=0x888d20, block=<value optimized out>, dispatch=<value optimized out>, self=<value optimized out>)
    at /build/buildd/glib2.0-2.22.2/glib/gmain.c:2591
#13 0x00007fb7558746b0 in IA__g_main_context_iteration (context=0x888d20, may_block=1) at /build/buildd/glib2.0-2.22.2/glib/gmain.c:2654
#14 0x00007fb75bee61a6 in QEventDispatcherGlib::processEvents (this=0x86be90, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#15 0x00007fb75c6564be in QGuiEventDispatcherGlib::processEvents (this=0xf12100, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#16 0x00007fb75bebc532 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#17 0x00007fb75bebc904 in QEventLoop::exec (this=0x7fff014f51b0, flags=) at kernel/qeventloop.cpp:201
#18 0x00007fb75bebeab9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#19 0x00007fb75fc61094 in kdemain () from /usr/lib/libkdeinit4_kwin.so
#20 0x00007fb75f8cbabd in __libc_start_main () from /lib/libc.so.6
#21 0x0000000000400679 in _start ()

Reported using DrKonqi