Version:           unknown (using KDE 3.5.5, Kubuntu (edgy) 4:3.5.5-0ubuntu3)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.17-10-generic

This were the last steps before Kontact crashed:
I checked email in "dimap account 2" and a local filter moved an email to a folder of "dimap account 1". I manually moved it back. Then checking mail in "dimap account 1" crashed:

Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1242293456 (LWP 5380)]
[New Thread -1281942624 (LWP 5384)]
[New Thread -1273549920 (LWP 5383)]
[New Thread -1265157216 (LWP 5382)]
[New Thread -1256764512 (LWP 5381)]
[KCrash handler]
#6  0x2d580a0d in ?? ()
#7  0xb55e9f7a in KMFolderImap::flagsToStatus (msg=0x9d55588, flags=1, 
    newMsg=true) at /build/buildd/kdepim-3.5.5/./kmail/kmfolderimap.cpp:1407
#8  0xb5606f33 in KMFolderCachedImap::slotGetMessagesData (this=0x86530b8, 
    job=0xaba59f0, data=@0xbfc94db0)
    at /build/buildd/kdepim-3.5.5/./kmail/kmfoldercachedimap.cpp:1465
#9  0xb5608532 in KMFolderCachedImap::qt_invoke (this=0x86530b8, _id=9, 
    _o=0xbfc94ab0) at ./kmfoldercachedimap.moc:372
#10 0xb6fbc957 in QObject::activate_signal (this=0xaba59f0, clist=0xa03d200, 
    o=0xbfc94ab0) at kernel/qobject.cpp:2356
#11 0xb6a9fbfd in KIO::TransferJob::data (this=0xaba59f0, t0=0xaba59f0, 
    t1=@0xbfc94db0) at ./jobclasses.moc:993
#12 0xb6a9fc78 in KIO::TransferJob::slotData (this=0xaba59f0, 
    _data=@0xbfc94db0) at /build/buildd/kdelibs-3.5.5/./kio/kio/job.cpp:906
#13 0xb6add6d9 in KIO::TransferJob::qt_invoke (this=0xaba59f0, _id=18, 
    _o=0xbfc94ba4) at ./jobclasses.moc:1072
#14 0xb6fbc957 in QObject::activate_signal (this=0xa688578, clist=0x9fb58d0, 
    o=0xbfc94ba4) at kernel/qobject.cpp:2356
#15 0xb6a9c41e in KIO::SlaveInterface::data (this=0xa688578, t0=@0xbfc94db0)
    at ./slaveinterface.moc:194
#16 0xb6afd3c3 in KIO::SlaveInterface::dispatch (this=0xa688578, _cmd=100, 
    rawdata=@0xbfc94db0)
    at /build/buildd/kdelibs-3.5.5/./kio/kio/slaveinterface.cpp:234
#17 0xb6afb75a in KIO::SlaveInterface::dispatch (this=0xa688578)
    at /build/buildd/kdelibs-3.5.5/./kio/kio/slaveinterface.cpp:173
#18 0xb6aac43c in KIO::Slave::gotInput (this=0xa688578)
    at /build/buildd/kdelibs-3.5.5/./kio/kio/slave.cpp:300
#19 0xb6aeb360 in KIO::Slave::qt_invoke (this=0xa688578, _id=4, _o=0xbfc94ed8)
    at ./slave.moc:113
#20 0xb6fbc957 in QObject::activate_signal (this=0xa60a9e0, clist=0x9364ec8, 
    o=0xbfc94ed8) at kernel/qobject.cpp:2356
#21 0xb6fbd26e in QObject::activate_signal (this=0xa60a9e0, signal=2, 
    param=30) at kernel/qobject.cpp:2449
#22 0xb7349cdb in QSocketNotifier::activated (this=0xa60a9e0, t0=30)
    at .moc/debug-shared-mt/moc_qsocketnotifier.cpp:85
#23 0xb6fdf516 in QSocketNotifier::event (this=0xa60a9e0, e=0xbfc95208)
    at kernel/qsocketnotifier.cpp:258
#24 0xb6f53b88 in QApplication::internalNotify (this=0xbfc95500, 
    receiver=0xa60a9e0, e=0xbfc95208) at kernel/qapplication.cpp:2635
#25 0xb6f559b7 in QApplication::notify (this=0xbfc95500, receiver=0xa60a9e0, 
    e=0xbfc95208) at kernel/qapplication.cpp:2358
#26 0xb767cdb2 in KApplication::notify (this=0xbfc95500, receiver=0xa60a9e0, 
    event=0xbfc95208)
    at /build/buildd/kdelibs-3.5.5/./kdecore/kapplication.cpp:550
#27 0xb6ee6389 in QApplication::sendEvent (receiver=0xa60a9e0, 
    event=0xbfc95208) at ../include/qapplication.h:520
#28 0xb6f45f81 in QEventLoop::activateSocketNotifiers (this=0x809e3c8)
    at kernel/qeventloop_unix.cpp:578
#29 0xb6efaea7 in QEventLoop::processEvents (this=0x809e3c8, flags=4)
    at kernel/qeventloop_x11.cpp:383
#30 0xb6f6e25e in QEventLoop::enterLoop (this=0x809e3c8)
    at kernel/qeventloop.cpp:198
#31 0xb6f6e06e in QEventLoop::exec (this=0x809e3c8)
    at kernel/qeventloop.cpp:145
#32 0xb6f55731 in QApplication::exec (this=0xbfc95500)
    at kernel/qapplication.cpp:2758
#33 0x0805ad81 in main (argc=1, argv=0xb55facc0)
    at /build/buildd/kdepim-3.5.5/./kontact/src/main.cpp:161
#34 0xb771a8cc in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#35 0x08058311 in _start ()

I also attached gdb and found that the KMMsgBase pointer must be the problem:
(gdb) frame 7
#7  0xb55e9f7a in KMFolderImap::flagsToStatus (msg=0x9d55588, flags=1, newMsg=true) at /build/buildd/kdepim-3.5.5/./kmail/kmfolderimap.cpp:1407
(gdb) print msg
$1 = (class KMMsgBase *) 0x9d55588
(gdb) print msg->isOfUnknownStatus()

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1242293456 (LWP 5380)]
0x2d580a0d in ?? ()

(gdb) frame 9
#9  0xb55e9f7a in KMFolderImap::flagsToStatus (msg=0x9d55588, flags=1, newMsg=true) at /build/buildd/kdepim-3.5.5/./kmail/kmfolderimap.cpp:1407
(gdb) print msg->status()

Program received signal SIGSEGV, Segmentation fault.
0x0005ad43 in ?? ()