Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.3.5 (KDE 4.3.5) "release 0"
Qt Version: 4.5.3
Operating System: Linux 2.6.31.12-0.1-desktop x86_64
Distribution: "openSUSE 11.3 (x86_64)"

What I was doing when the application crashed:
Unfortunately, I can't reproduce it easily, but what I can say is that Plasma always becomes very unstable after using multiscreen (with nvidia driver).

The panel even never reappears when using an external screen position over than right of the main screen.

 -- Backtrace:
Application: Espace de travail Plasma (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0x7fda4cde1750 (LWP 28699))]

Thread 2 (Thread 0x7fda2d9e2910 (LWP 28700)):
#0  0x00007fda4c5c5049 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007fda4c83553b in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib64/libQtCore.so.4
#2  0x00007fda48d069ec in ?? () from /usr/lib64/libQtNetwork.so.4
#3  0x00007fda4c834485 in ?? () from /usr/lib64/libQtCore.so.4
#4  0x00007fda4c5c065d in start_thread () from /lib64/libpthread.so.0
#5  0x00007fda49fcbe1d in clone () from /lib64/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7fda4cde1750 (LWP 28699)):
[KCrash Handler]
#5  0x00007fda44560e44 in Plasma::ExtenderItem::group() const () from /usr/lib64/libplasma.so.3
#6  0x00007fda4455f658 in Plasma::ExtenderGroup::items() const () from /usr/lib64/libplasma.so.3
#7  0x00007fda2f77a323 in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#8  0x00007fda2f77ad10 in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#9  0x00007fda4c92efbc in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib64/libQtCore.so.4
#10 0x00007fda2f77b452 in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#11 0x00007fda2f77c6c4 in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#12 0x00007fda4c92efbc in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib64/libQtCore.so.4
#13 0x00007fda2f77d617 in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#14 0x00007fda2f77daeb in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#15 0x00007fda2f78b31a in Plasma::Theme::font(Plasma::Theme::FontRole) const () from /usr/lib64/kde4/plasma_applet_systemtray.so
#16 0x00007fda4c9292fd in QObject::event(QEvent*) () from /usr/lib64/libQtCore.so.4
#17 0x00007fda4a7022ac in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQtGui.so.4
#18 0x00007fda4a70957e in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQtGui.so.4
#19 0x00007fda4b2fd016 in KApplication::notify(QObject*, QEvent*) () from /usr/lib64/libkdeui.so.5
#20 0x00007fda4c919ddc in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib64/libQtCore.so.4
#21 0x00007fda4c91a9ea in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib64/libQtCore.so.4
#22 0x00007fda4c942803 in ?? () from /usr/lib64/libQtCore.so.4
#23 0x00007fda4964bdee in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#24 0x00007fda4964f7b8 in ?? () from /usr/lib64/libglib-2.0.so.0
#25 0x00007fda4964f8e0 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#26 0x00007fda4c9423a3 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQtCore.so.4
#27 0x00007fda4a79531e in ?? () from /usr/lib64/libQtGui.so.4
#28 0x00007fda4c918712 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQtCore.so.4
#29 0x00007fda4c918ae4 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQtCore.so.4
#30 0x00007fda4c91ac99 in QCoreApplication::exec() () from /usr/lib64/libQtCore.so.4
#31 0x00007fda40e44e3f in kdemain () from /usr/lib64/libkdeinit4_plasma-desktop.so
#32 0x0000000000406f88 in _start ()

Reported using DrKonqi