Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.2.96 (KDE 4.2.96 (KDE 4.3 RC2))
Qt Version: 4.5.0
Operating System: Linux 2.6.28-14-generic x86_64
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
This happed while adding and removing several applets to the panel.

1.) Upgraded from kde 4.3 rc1 to kde4.3rc2 (ubuntu backports)
2.) Reboot && Login && Automatic Configuration Conversion
3.) Activated the Panel configuration (butt on the left border of the panel)
4.) added and removed several applets

 -- Backtrace:
Application: Plasma Workspace (kdeinit4), signal: Segmentation fault
[Current thread is 0 (LWP 4559)]

Thread 2 (Thread 0x7f8cb9e76950 (LWP 4573)):
#0  0x00007f8cd54b72e9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007f8cd9633939 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#2  0x00007f8cd84af4cc in ?? () from /usr/lib/libQtNetwork.so.4
#3  0x00007f8cd9632952 in ?? () from /usr/lib/libQtCore.so.4
#4  0x00007f8cd54b33ba in start_thread () from /lib/libpthread.so.0
#5  0x00007f8cd6097fcd in clone () from /lib/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f8cd9bf5750 (LWP 4559)):
[KCrash Handler]
#5  0x00007f8cd7268294 in QGraphicsItem::isWidget () from /usr/lib/libQtGui.so.4
#6  0x00007f8cd726ad49 in QGraphicsItem::isWindow () from /usr/lib/libQtGui.so.4
#7  0x00007f8cd729d0f1 in QGraphicsScene::event () from /usr/lib/libQtGui.so.4
#8  0x00007f8cd6ca478d in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#9  0x00007f8cd6cac97a in QApplication::notify () from /usr/lib/libQtGui.so.4
#10 0x00007f8cd7de763b in KApplication::notify () from /usr/lib/libkdeui.so.5
#11 0x00007f8cd971b75c in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#12 0x00007f8cd72abde6 in QGraphicsView::viewportEvent () from /usr/lib/libQtGui.so.4
#13 0x00007f8cd971aa68 in QCoreApplicationPrivate::sendThroughObjectEventFilters () from /usr/lib/libQtCore.so.4
#14 0x00007f8cd6ca475c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#15 0x00007f8cd6cac97a in QApplication::notify () from /usr/lib/libQtGui.so.4
#16 0x00007f8cd7de763b in KApplication::notify () from /usr/lib/libkdeui.so.5
#17 0x00007f8cd971b75c in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#18 0x00007f8cd6cf5a3a in QWidget::event () from /usr/lib/libQtGui.so.4
#19 0x00007f8cd708f40b in QFrame::event () from /usr/lib/libQtGui.so.4
#20 0x00007f8cd7120949 in QAbstractScrollArea::event () from /usr/lib/libQtGui.so.4
#21 0x00007f8cd6ca478d in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#22 0x00007f8cd6cac97a in QApplication::notify () from /usr/lib/libQtGui.so.4
#23 0x00007f8cd7de763b in KApplication::notify () from /usr/lib/libkdeui.so.5
#24 0x00007f8cd971b75c in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#25 0x00007f8cd6cab495 in QApplication::setActiveWindow () from /usr/lib/libQtGui.so.4
#26 0x00007f8cd6d14e2d in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#27 0x00007f8cd6d3d464 in ?? () from /usr/lib/libQtGui.so.4
#28 0x00007f8cd570220a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#29 0x00007f8cd57058e0 in ?? () from /usr/lib/libglib-2.0.so.0
#30 0x00007f8cd5705a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#31 0x00007f8cd9744e6f in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#32 0x00007f8cd6d3cbef in ?? () from /usr/lib/libQtGui.so.4
#33 0x00007f8cd971a002 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#34 0x00007f8cd971a3cd in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#35 0x00007f8cd971c694 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#36 0x00007f8cce83c6bb in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#37 0x0000000000407215 in _start ()

Reported using DrKonqi