Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.3.2 (KDE 4.3.2)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-17-generic x86_64
Distribution: Ubuntu 9.10

What I was doing when the application crashed:
I simply right clicked on the kde desktop to cause this error.  Approximately 30 min prior, alt-tab mysteriously stopped working.  After the gui crash, alt-tab is still "broken".  I am not sure if the alt-tab issue is related or not, but it seemed strange so I mentioned it here.

 -- Backtrace:
Application: Plasma Workspace (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0x7f4d3462e750 (LWP 1886))]

Thread 2 (Thread 0x7f4d1333f910 (LWP 1889)):
#0  0x00007f4d30de75a9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007f4d3406d4fb in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQtCore.so.4
#2  0x00007f4d304a478c in ?? () from /usr/lib/libQtNetwork.so.4
#3  0x00007f4d3406c445 in ?? () from /usr/lib/libQtCore.so.4
#4  0x00007f4d30de2a04 in start_thread () from /lib/libpthread.so.0
#5  0x00007f4d319c280d in clone () from /lib/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f4d3462e750 (LWP 1886)):
[KCrash Handler]
#5  0x00007f4d32683484 in QGraphicsItem::isWidget() const () from /usr/lib/libQtGui.so.4
#6  0x00007f4d32685b89 in QGraphicsItem::isWindow() const () from /usr/lib/libQtGui.so.4
#7  0x00007f4d326b9269 in QGraphicsScene::event(QEvent*) () from /usr/lib/libQtGui.so.4
#8  0x00007f4d32102efc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#9  0x00007f4d3210a1ce in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#10 0x00007f4d32d39ab6 in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#11 0x00007f4d34152c2c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#12 0x00007f4d326ca9f6 in QGraphicsView::viewportEvent(QEvent*) () from /usr/lib/libQtGui.so.4
#13 0x00007f4d34151f47 in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#14 0x00007f4d32102ecc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#15 0x00007f4d3210a1ce in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#16 0x00007f4d32d39ab6 in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#17 0x00007f4d34152c2c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#18 0x00007f4d32151b6b in QWidget::event(QEvent*) () from /usr/lib/libQtGui.so.4
#19 0x00007f4d324ad2a6 in QFrame::event(QEvent*) () from /usr/lib/libQtGui.so.4
#20 0x00007f4d3253cbc9 in QAbstractScrollArea::event(QEvent*) () from /usr/lib/libQtGui.so.4
#21 0x00007f4d32102efc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#22 0x00007f4d3210a1ce in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#23 0x00007f4d32d39ab6 in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#24 0x00007f4d34152c2c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#25 0x00007f4d3210d55b in QApplication::setActiveWindow(QWidget*) () from /usr/lib/libQtGui.so.4
#26 0x00007f4d3216eb9e in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/libQtGui.so.4
#27 0x00007f4d32197d0c in ?? () from /usr/lib/libQtGui.so.4
#28 0x00007f4d31033bce in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#29 0x00007f4d31037598 in ?? () from /lib/libglib-2.0.so.0
#30 0x00007f4d310376c0 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#31 0x00007f4d3417b1a6 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#32 0x00007f4d321974be in ?? () from /usr/lib/libQtGui.so.4
#33 0x00007f4d34151532 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#34 0x00007f4d34151904 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#35 0x00007f4d34153ab9 in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#36 0x00007f4d284d44cf in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#37 0x0000000000406da8 in _start ()

Reported using DrKonqi