Version:            (using KDE 4.0.0)
Installed from:    Gentoo Packages
Compiler:          GCC version 4.1.2 
OS:                Linux

Plasma crashed on KmPlot launch, with the following back trace:
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0x2b55edfc1f30 (LWP 5814)]
[New Thread 0x40804950 (LWP 5816)]
[KCrash handler]
#5  0x00002b55e645d940 in KSycocaEntry::entryPath ()
   from /usr/kde/4.0/lib64/libkdecore.so.5
#6  0x00002aaaabc3cd46 in Kickoff::RecentlyUsedModel::recentApplicationRemoved
    () from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#7  0x00002aaaabc3e290 in Kickoff::RecentlyUsedModel::qt_metacall ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#8  0x00002b55e9641fe8 in QMetaObject::activate ()
   from /usr/lib64/qt4/libQtCore.so.4
#9  0x00002aaaabc388b5 in Kickoff::RecentApplications::applicationRemoved ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#10 0x00002aaaabc3abae in Kickoff::RecentApplications::Private::addEntry ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#11 0x00002aaaabc38e33 in Kickoff::RecentApplications::add ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#12 0x00002aaaabc4630b in Kickoff::ServiceItemHandler::openUrl ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#13 0x00002aaaabc451f6 in Kickoff::UrlItemLauncher::Private::openUrl ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#14 0x00002aaaabc448ac in Kickoff::UrlItemLauncher::openItem ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#15 0x00002aaaabc4e428 in Kickoff::Launcher::eventFilter ()
   from /usr/kde/4.0/lib64/kde4/plasma_applet_launcher.so
#16 0x00002b55ea13f5e2 in QApplicationPrivate::notify_helper ()
   from /usr/lib64/qt4/libQtGui.so.4
#17 0x00002b55ea141cfe in QApplication::notify ()
   from /usr/lib64/qt4/libQtGui.so.4
#18 0x00002b55e68aa2cb in KApplication::notify ()
   from /usr/kde/4.0/lib64/libkdeui.so.5
#19 0x00002b55e96310f0 in QCoreApplication::notifyInternal ()
   from /usr/lib64/qt4/libQtCore.so.4
#20 0x00002b55ea195286 in QETWidget::translateMouseEvent ()
   from /usr/lib64/qt4/libQtGui.so.4
#21 0x00002b55ea194025 in QApplication::x11ProcessEvent ()
   from /usr/lib64/qt4/libQtGui.so.4
#22 0x00002b55ea1b5ff5 in QEventDispatcherX11::processEvents ()
   from /usr/lib64/qt4/libQtGui.so.4
#23 0x00002b55e9630788 in QEventLoop::processEvents ()
   from /usr/lib64/qt4/libQtCore.so.4
#24 0x00002b55e9630899 in QEventLoop::exec ()
   from /usr/lib64/qt4/libQtCore.so.4
#25 0x00002b55e96326fe in QCoreApplication::exec ()
   from /usr/lib64/qt4/libQtCore.so.4
#26 0x00002b55e5b09644 in kdemain ()
   from /usr/kde/4.0/lib64/libkdeinit4_plasma.so
#27 0x00002b55eb7efb74 in __libc_start_main () from /lib64/libc.so.6
#28 0x00000000004008b9 in _start ()
#0  0x00002b55eb8647e1 in nanosleep () from /lib64/libc.so.6


I've haven't been able to reproduce this bug, but on try, I launched the Graph application, which crashed KDE - only remaining a firefox window, and a blue background with no functionality.