Version:            (using KDE 4.2.1)
Installed from:    Ubuntu Packages

kmail was running minimized and checking for mail when it crashed. here's the trace:

Application: Kontact (kontact), signal SIGABRT
[Current thread is 0 (LWP 6945)]

Thread 1 (Thread 0xb4b176c0 (LWP 6945)):
[KCrash Handler]
#6  0xb7fe7430 in __kernel_vsyscall ()
#7  0xb59b58a0 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb59b7268 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb5c5a795 in qt_message_output () from /usr/lib/libQtCore.so.4
#10 0xb5c5a872 in qFatal () from /usr/lib/libQtCore.so.4
#11 0xb5c5a915 in qt_assert () from /usr/lib/libQtCore.so.4
#12 0xb1420c81 in FolderStorage::ignoreJobsForMessage (this=0xa5f2a98, msg=0xa7b6af0) at /usr/include/qt4/QtCore/qlist.h:246
#13 0xb141f443 in FolderStorage::unGetMsg (this=0xa5f2a98, idx=0) at /build/buildd/kdepim-4.2.1/kmail/folderstorage.cpp:569
#14 0xb13ec7db in KMFolder::unGetMsg (this=0xa619178, idx=0) at /build/buildd/kdepim-4.2.1/kmail/kmfolder.cpp:372
#15 0xb146f392 in KMSearchPattern::matches (this=0xa640260, serNum=176384812, ignoreBody=false) at /build/buildd/kdepim-4.2.1/kmail/kmsearchpattern.cpp:794
#16 0xb141edf0 in FolderStorage::slotProcessNextSearchBatch (this=0xa5f2a98) at /build/buildd/kdepim-4.2.1/kmail/folderstorage.cpp:1171
#17 0xb1639844 in KMSearch::slotProcessNextBatch (this=0xa5b4270) at /build/buildd/kdepim-4.2.1/kmail/kmfoldersearch.cpp:272
#18 0xb16399bb in KMSearch::qt_metacall (this=0xa5b4270, _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0xbfce7a48) at /build/buildd/kdepim-4.2.1/obj-i486-linux-gnu/kmail/kmfoldersearch.moc:78
#19 0xb5d67a60 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#20 0xb5d687e2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#21 0xb5da27a7 in QTimer::timeout () from /usr/lib/libQtCore.so.4
#22 0xb5d6e40e in QTimer::timerEvent () from /usr/lib/libQtCore.so.4
#23 0xb5d6253f in QObject::event () from /usr/lib/libQtCore.so.4
#24 0xb62058ec in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#25 0xb620d72e in QApplication::notify () from /usr/lib/libQtGui.so.4
#26 0xb6d1f10d in KApplication::notify (this=0xbfce8188, receiver=0xa5f28f0, event=0xbfce7edc) at /build/buildd/kde4libs-4.2.1a/kdeui/kernel/kapplication.cpp:307
#27 0xb5d52e61 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#28 0xb5d80d81 in ?? () from /usr/lib/libQtCore.so.4
#29 0xb5d7d520 in ?? () from /usr/lib/libQtCore.so.4
#30 0xb502e6f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#31 0xb5031da3 in ?? () from /usr/lib/libglib-2.0.so.0
#32 0xb5031f61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#33 0xb5d7d478 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#34 0xb629fea5 in ?? () from /usr/lib/libQtGui.so.4
#35 0xb5d5152a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#36 0xb5d516ea in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#37 0xb5d53da5 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#38 0xb6205767 in QApplication::exec () from /usr/lib/libQtGui.so.4
#39 0x0804c072 in main (argc=1, argv=0xbfce8484) at /build/buildd/kdepim-4.2.1/kontact/src/main.cpp:218