Umbrello crash without no reason

Umbrello, the UML modeling tool for KDE, often crashes without reason.
Here is the stacktrace :

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Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
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`system-supplied DSO at 0xffffe000' has disappeared; keeping its symbols.
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[Thread debugging using libthread_db enabled]
[New Thread -1230554592 (LWP 12187)]
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[KCrash handler]
#4 0xb7a9c174 in KToolBarButton::slotClicked () from /usr/lib/libkdeui.so.4
#5 0xb7a9ca5f in KToolBarButton::qt_invoke () from /usr/lib/libkdeui.so.4
#6 0xb717cfdd in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#7 0xb717ceae in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#8 0xb749ef12 in QButton::clicked () from /usr/lib/libqt-mt.so.3
#9 0xb7208eae in QButton::mouseReleaseEvent () from /usr/lib/libqt-mt.so.3
#10 0xb7a9b0a1 in KToolBarButton::mouseReleaseEvent ()
   from /usr/lib/libkdeui.so.4
#11 0xb71b07e9 in QWidget::event () from /usr/lib/libqt-mt.so.3
#12 0xb7125370 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#13 0xb7124ac7 in QApplication::notify () from /usr/lib/libqt-mt.so.3
#14 0xb772d960 in KApplication::notify () from /usr/lib/libkdecore.so.4
#15 0xb70be12f in QETWidget::translateMouseEvent ()
   from /usr/lib/libqt-mt.so.3
#16 0xb70bbe1c in QApplication::x11ProcessEvent () from /usr/lib/libqt-mt.so.3
#17 0xb70d1ec2 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#18 0xb713674c in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#19 0xb713660e in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#20 0xb712557b in QApplication::exec () from /usr/lib/libqt-mt.so.3
#21 0x0814649a in main ()