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: 4.5.1
Operating System: Linux 2.6.28-13-generic x86_64
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
I'm using an NVidia GeForce 9400M videcard with proprietary drivers version 185.18.14.

Any time I take a screenshot, the display becomes severely corrupted and starts flickering. After doing that, I switched to the terminal and back to X, and KWin crashed. It looks like it's an NVidia bug, but since KWin crashed, I'm filing it here just in case.

 -- Backtrace:
Application: KWin (kwin), signal: Aborted
[KCrash Handler]
#5  0x00007ff0837c9fb5 in *__GI_raise (sig=<value optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#6  0x00007ff0837cbbc3 in *__GI_abort () at abort.c:88
#7  0x00007ff085114d09 in ?? () from /usr/lib/libGL.so.1
#8  0x00007ff07e1bd23e in ?? () from /usr/lib/libGLcore.so.1
#9  0x00007ff07e1bdc03 in ?? () from /usr/lib/libGLcore.so.1
#10 0x00007ff07df0f564 in ?? () from /usr/lib/libGLcore.so.1
#11 0x00007ff07db90666 in ?? () from /usr/lib/libGLcore.so.1
#12 0x00007ff088cc3d43 in KWin::SceneOpenGL::flushBuffer (this=0x17b13c0, mask=<value optimized out>, damage=
        {d = 0x32995a0, static shared_empty = {ref = {_q_value = 7422}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}}) at /build/buildd/kdebase-workspace-4.2.96/kwin/scene_opengl.cpp:831
#13 0x00007ff088cc5986 in KWin::SceneOpenGL::paint (this=0x17b13c0, damage={d = 0x7fff91115a20, static shared_empty = {ref = {_q_value = 7422}, rgn = 0x0, xrectangles = 0x0, qt_rgn = 0x0}}, 
    toplevels=<value optimized out>) at /build/buildd/kdebase-workspace-4.2.96/kwin/scene_opengl.cpp:759
#14 0x00007ff088cb22f6 in KWin::Workspace::performCompositing (this=0x17dd000) at /build/buildd/kdebase-workspace-4.2.96/kwin/composite.cpp:420
#15 0x00007ff088c4de8a in KWin::Workspace::qt_metacall (this=0x17dd000, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff91115bb0)
    at /build/buildd/kdebase-workspace-4.2.96/obj-x86_64-linux-gnu/kwin/workspace.moc:473
#16 0x00007ff0863648d2 in QMetaObject::activate (sender=0x17dd428, from_signal_index=<value optimized out>, to_signal_index=4, argv=0xffffffffffffffff) at kernel/qobject.cpp:3120
#17 0x00007ff08635ebb3 in QObject::event (this=0x17dd428, e=0x3a95) at kernel/qobject.cpp:1082
#18 0x00007ff086a58b9d in QApplicationPrivate::notify_helper (this=0x1595fc0, receiver=0x17dd428, e=0x7fff91116260) at kernel/qapplication.cpp:4057
#19 0x00007ff086a60dea in QApplication::notify (this=0x7fff911165d0, receiver=0x17dd428, e=0x7fff91116260) at kernel/qapplication.cpp:4022
#20 0x00007ff087fc163b in KApplication::notify (this=0x7fff911165d0, receiver=0x17dd428, event=0x7fff91116260) at /build/buildd/kde4libs-4.2.96/kdeui/kernel/kapplication.cpp:302
#21 0x00007ff08634edfc in QCoreApplication::notifyInternal (this=0x7fff911165d0, receiver=0x17dd428, event=0x7fff91116260) at kernel/qcoreapplication.cpp:610
#22 0x00007ff08637beb6 in QTimerInfoList::activateTimers (this=0x1599c20) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#23 0x00007ff0863785cd in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:164
#24 0x00007ff07f67e20a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#25 0x00007ff07f6818e0 in ?? () from /usr/lib/libglib-2.0.so.0
#26 0x00007ff07f681a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#27 0x00007ff08637852f in QEventDispatcherGlib::processEvents (this=0x157cfe0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:324
#28 0x00007ff086af170f in QGuiEventDispatcherGlib::processEvents (this=0x3a95, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#29 0x00007ff08634d6a2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = -1861131056}) at kernel/qeventloop.cpp:149
#30 0x00007ff08634da6d in QEventLoop::exec (this=0x7fff91116510, flags={i = -1861130976}) at kernel/qeventloop.cpp:200
#31 0x00007ff08634fd34 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#32 0x00007ff088c66048 in kdemain (argc=3, argv=0x7fff91116ab8) at /build/buildd/kdebase-workspace-4.2.96/kwin/main.cpp:527
#33 0x00007ff0837b55a6 in __libc_start_main (main=0x4008c0 <main>, argc=3, ubp_av=0x7fff91116ab8, init=0x4008f0 <__libc_csu_init>, fini=<value optimized out>, rtld_fini=<value optimized out>, 
    stack_end=0x7fff91116aa8) at libc-start.c:220
#34 0x00000000004007f9 in _start () at ../sysdeps/x86_64/elf/start.S:113

Reported using DrKonqi