Kontact Debian Sarge (ia32) 
Qt: 3.3.4
KDE: 3.3.2
Kontact: 1.0 (proko2 branch after 2.1.2) Revision 571078

I was pressing apply after having removed two online imap accounts.

Last words on the command line:

kmail: WARNING: IMAPRightsToPermission: found read (r) but not seen (s). Thingswill not work well for folder newimaps://proko2test1%40test.hq@neso.test.hq:993/user/crypto1/rein/ and user crypto3@test.hq
kmail: WARNING: Ask your admin for 's' permissions.
kmail: WARNING: IMAPRightsToPermission: found read (r) but not seen (s). Thingswill not work well for folder newimaps://proko2test1%40test.hq@neso.test.hq:993/user/crypto1/rein/ and user proko2test4@test.hq
kmail: WARNING: Ask your admin for 's' permissions.
kmail: WARNING: Can not find parent folder
*** KMail got signal 11 (Crashing)

Backtrace:

Using host libthread_db library "/lib/tls/libthread_db.so.1".
`system-supplied DSO at 0xfbffd000' has disappeared; keeping its symbols.
[Thread debugging using libthread_db enabled]
[New Thread 1099268352 (LWP 27526)]
[KCrash handler]
#3  0x41efb248 in KMFolderTree::slotFolderExpanded ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#4  0x41efdadc in KMFolderTree::qt_invoke ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#5  0x40f3d71c in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#6  0x4128f5fd in QListView::expanded () from /usr/lib/libqt-mt.so.3
#7  0x4101b017 in QListViewItem::setOpen () from /usr/lib/libqt-mt.so.3
#8  0x41ef7249 in KMFolderTree::addDirectory ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#9  0x41ef6ac8 in KMFolderTree::reload ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#10 0x41ef745a in KMFolderTree::doFolderListChanged ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#11 0x41efda7e in KMFolderTree::qt_invoke ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#12 0x40f3d71c in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#13 0x40f3d544 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#14 0x41f8e4bb in KMFolderMgr::changed ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#15 0x41f8d5e8 in KMFolderMgr::contentsChanged ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#16 0x41f8d37f in KMFolderMgr::removeFolderAux ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#17 0x41f8eba1 in KMFolderMgr::qt_invoke ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#18 0x40f3d71c in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#19 0x41f4ccac in KMFolder::removed ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#20 0x41f4cfe2 in KMFolder::qt_emit ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#21 0x40f3d751 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#22 0x41f6ae1c in FolderStorage::removed ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#23 0x41f69322 in FolderStorage::remove ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#24 0x41fe689d in KMFolderImap::remove ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#25 0x41f4abe7 in KMFolder::remove ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#26 0x41f8d025 in KMFolderMgr::removeFolder ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#27 0x41f8cfd0 in KMFolderMgr::remove ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#28 0x4201ab08 in KMKernel::cleanupImapFolders ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#29 0x41e9d064 in NetworkPageReceivingTab::save ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#30 0x41ec419a in ConfigModuleWithTabs::save ()
   from /opt/kolab-client-build/kde3.3+proko2+aegypten2/install/lib/libkmailprivate.so.0
#31 0x4005043b in KCModuleProxy::save () from /usr/lib/libkutils.so.1
#32 0x4004594e in KCMultiDialog::apply () from /usr/lib/libkutils.so.1
#33 0x40045b7a in KCMultiDialog::slotOk () from /usr/lib/libkutils.so.1
#34 0x408b7a47 in KDialogBase::qt_invoke () from /usr/lib/libkdeui.so.4
#35 0x400442a3 in KCMultiDialog::qt_invoke () from /usr/lib/libkutils.so.1
#36 0x40f3d71c in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#37 0x40f3d544 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#38 0x4128382e in QButton::clicked () from /usr/lib/libqt-mt.so.3
#39 0x40fcff94 in QButton::mouseReleaseEvent () from /usr/lib/libqt-mt.so.3
#40 0x40f73b37 in QWidget::event () from /usr/lib/libqt-mt.so.3
#41 0x40ee0e1f in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#42 0x40ee0514 in QApplication::notify () from /usr/lib/libqt-mt.so.3
#43 0x40a7aec3 in KApplication::notify () from /usr/lib/libkdecore.so.4
#44 0x40e755b0 in QETWidget::translateMouseEvent () from /usr/lib/libqt-mt.so.3
#45 0x40e7323e in QApplication::x11ProcessEvent () from /usr/lib/libqt-mt.so.3
#46 0x40e8a254 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#47 0x40ef31d8 in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#48 0x40ef3088 in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#49 0x40ee1071 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#50 0x08059c5b in main ()