Version:           Kontact 1.2.9 / KMail 1.9.9 (using KDE 4.0.3)
Installed from:    Ubuntu Packages
OS:                Linux

I tried bogofilters for my spam since yesterday, today I marked one Mail (in an IMAP subfolder) as Spam with the new buttons in Kontact/KMail. Undo crashed kontact. reproduceable.

KDE-Crashmanager Backtrace:
{snip}
[Thread debugging using libthread_db enabled]
[New Thread 0xb5f25920 (LWP 6134)]
[New Thread 0xb3879b90 (LWP 6138)]
[New Thread 0xb407ab90 (LWP 6137)]
[New Thread 0xb487bb90 (LWP 6136)]
[New Thread 0xb507cb90 (LWP 6135)]
{snip}
[KCrash handler]
#6  0xb53fd429 in KMFolder::moveMsg () from /usr/lib/libkmailprivate.so
#7  0xb54bc904 in KMail::UndoStack::undo () from /usr/lib/libkmailprivate.so
#8  0xb53b9ad5 in KMHeaders::undo () from /usr/lib/libkmailprivate.so
#9  0xb558b67b in KMMainWidget::slotUndo () from /usr/lib/libkmailprivate.so
#10 0xb5591d72 in KMMainWidget::qt_invoke () from /usr/lib/libkmailprivate.so
#11 0xb67e0704 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#12 0xb67e11e9 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#13 0xb711bb19 in KAction::activated () from /usr/lib/libkdeui.so.4
#14 0xb715c452 in KAction::slotActivated () from /usr/lib/libkdeui.so.4
#15 0xb724794d in KAction::slotPopupActivated () from /usr/lib/libkdeui.so.4
#16 0xb7247c33 in KAction::qt_invoke () from /usr/lib/libkdeui.so.4
#17 0xb67e0704 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#18 0xb6b6faba in QSignal::signal () from /usr/lib/libqt-mt.so.3
#19 0xb67ff7b2 in QSignal::activate () from /usr/lib/libqt-mt.so.3
#20 0xb6904690 in QPopupMenu::mouseReleaseEvent () from /usr/lib/libqt-mt.so.3
#21 0xb7122a12 in KPopupMenu::mouseReleaseEvent () from /usr/lib/libkdeui.so.4
#22 0xb6816e33 in QWidget::event () from /usr/lib/libqt-mt.so.3
#23 0xb6774c36 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#24 0xb6776de5 in QApplication::notify () from /usr/lib/libqt-mt.so.3
#25 0xb6f35672 in KApplication::notify () from /usr/lib/libkdecore.so.4
#26 0xb6705301 in QApplication::sendSpontaneousEvent ()
   from /usr/lib/libqt-mt.so.3
#27 0xb6703c6a in QETWidget::translateMouseEvent ()
   from /usr/lib/libqt-mt.so.3
#28 0xb670212f in QApplication::x11ProcessEvent () from /usr/lib/libqt-mt.so.3
#29 0xb6719943 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#30 0xb678ff90 in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#31 0xb678fc8e in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#32 0xb67767df in QApplication::exec () from /usr/lib/libqt-mt.so.3
#33 0x0805c113 in ?? ()
#34 0xbf9deafc in ?? ()
#35 0x00000001 in ?? ()
#36 0x00000001 in ?? ()
#37 0x00000000 in ?? ()

-----------

When I tag an Mail as "important", And I tried to undo this  (still with bogofilter) Kontact/KMail crashes again.

Deleting all filter (Icons for Spam and Ham disappear) an undo for a important-mark is commented with "Es kann nichts rückgängig gemacht werden." Kontact/KMail stays alive.