Version:            (using KDE 4.2.0)
Compiler:          gcc version 4.3.3 x86_64-unknown-linux-gnu
OS:                Linux
Installed from:    Unlisted Binary Package

I'm using Arch Linux x86_64 with xorg-server-1.5.3-4 and video driver nvidia-180.22-1.

After upgrading from package kdebase-4.2.0-1 to kdebase-4.2.1-1 (the other kde packages were updated, too), kwin frequently crashes when activating the "present windows" effect, especially often when the system load is high.
When it isn't, "present windows" works most of the time.

Before the update the effect worked fine.

After the crash, Kwin restarts and shows the following backtrace:

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Application: KWin (kwin), signal SIGSEGV
0x00007fac41c48fd0 in __nanosleep_nocancel () from /lib/libc.so.6

Thread 1 (Thread 0x7fac46e84790 (LWP 5873)):
[KCrash Handler]
#5  0x00007fac3b25a360 in KWin::PresentWindowsEffect::setHighlightedWindow () from /usr/lib/kde4/kwin4_effect_builtins.so
#6  0x00007fac3b26535f in KWin::PresentWindowsEffect::rearrangeWindows () from /usr/lib/kde4/kwin4_effect_builtins.so
#7  0x00007fac3b265e91 in KWin::PresentWindowsEffect::setActive () from /usr/lib/kde4/kwin4_effect_builtins.so
#8  0x00007fac3b2666cb in KWin::PresentWindowsEffect::qt_metacall () from /usr/lib/kde4/kwin4_effect_builtins.so
#9  0x00007fac448a4d30 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#10 0x00007fac44f45367 in QAction::triggered () from /usr/lib/libQtGui.so.4
#11 0x00007fac44f45b24 in QAction::activate () from /usr/lib/libQtGui.so.4
#12 0x00007fac46313385 in KGlobalAccelPrivate::_k_invokeAction () from /usr/lib/libkdeui.so.5
#13 0x00007fac4631705e in KGlobalAccel::qt_metacall () from /usr/lib/libkdeui.so.5
#14 0x00007fac448a4d30 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#15 0x00007fac463196b4 in OrgKdeKdedGlobalAccelInterface::invokeAction () from /usr/lib/libkdeui.so.5
#16 0x00007fac4631a353 in OrgKdeKdedGlobalAccelInterface::qt_metacall () from /usr/lib/libkdeui.so.5
#17 0x00007fac44b7a283 in ?? () from /usr/lib/libQtDBus.so.4
#18 0x00007fac44b8036f in ?? () from /usr/lib/libQtDBus.so.4
#19 0x00007fac448a0fde in QObject::event () from /usr/lib/libQtCore.so.4
#20 0x00007fac44f4a4ed in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#21 0x00007fac44f5087a in QApplication::notify () from /usr/lib/libQtGui.so.4
#22 0x00007fac462d15cb in KApplication::notify () from /usr/lib/libkdeui.so.5
#23 0x00007fac44893401 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#24 0x00007fac44893dc7 in QCoreApplicationPrivate::sendPostedEvents () from /usr/lib/libQtCore.so.4
#25 0x00007fac448b7c33 in ?? () from /usr/lib/libQtCore.so.4
#26 0x00007fac3fab8aa2 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#27 0x00007fac3fabc21d in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#28 0x00007fac3fabc3db in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#29 0x00007fac448b78cf in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#30 0x00007fac44fcb04f in ?? () from /usr/lib/libQtGui.so.4
#31 0x00007fac44891d72 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#32 0x00007fac44891f05 in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#33 0x00007fac44894065 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#34 0x00007fac46b38607 in kdemain () from /usr/lib/libkdeinit4_kwin.so
#35 0x00007fac41bc8546 in __libc_start_main () from /lib/libc.so.6
#36 0x0000000000400829 in _start ()

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Thank you for your help,
Johannes