Version:            (using KDE KDE 3.5.5)
Installed from:    OpenBSD Packages
Compiler:          gcc version 3.3.5 (propolice) Thread model: single 
OS:                OpenBSD

Those crashes are reproduceable on KDE 3.5.4 too.
KMail crashes then:
1. new mail is incoming into mailbox
2. at the same time new messages change status to unreaded
After restarting of kmail those (now) unreaded mail messages disappears from mailbox.

Stacktrace below:
(no debugging symbols found)
[KCrash handler]
#12 0x0d0bdca5 in kill () from /usr/lib/libc.so.40.1
#13 0x0d0f65a3 in abort () at /usr/src/lib/libc/stdlib/abort.c:65
#14 0x1015df90 in __cxxabiv1::__terminate(void (*)()) ()
   from /usr/local/lib/libqt-mt.so.30.1
#15 0x1015dfc4 in std::terminate() () from /usr/local/lib/libqt-mt.so.30.1
#16 0x1015c69c in __cxa_pure_virtual () from /usr/local/lib/libqt-mt.so.30.1
#17 0x00fe5d15 in KMail::ImapJob::slotGetNextMessage() ()
   from /usr/local/lib/libkmailprivate.so
#18 0x00fe49f7 in KMail::ImapJob::init(KMail::FolderJob::JobType, QString, KMFolderImap*, QPtrList<KMMessage>&) () from /usr/local/lib/libkmailprivate.so
#19 0x00fe7a84 in KMail::ImapJob::execute() ()
   from /usr/local/lib/libkmailprivate.so
#20 0x00fdd0c1 in KMail::FolderJob::start() ()
   from /usr/local/lib/libkmailprivate.so
#21 0x00f30af3 in KMFolderImap::doCreateJob(KMMessage*, KMail::FolderJob::JobType, KMFolder*, QString, KMail::AttachmentStrategy const*) const ()
   from /usr/local/lib/libkmailprivate.so
#22 0x00eb6fb0 in FolderStorage::createJob(KMMessage*, KMail::FolderJob::JobType, KMFolder*, QString, KMail::AttachmentStrategy const*) const ()
   from /usr/local/lib/libkmailprivate.so
#23 0x00e9e5e1 in KMFolder::createJob(KMMessage*, KMail::FolderJob::JobType, KMFolder*, QString, KMail::AttachmentStrategy const*) const ()
   from /usr/local/lib/libkmailprivate.so
#24 0x00fc9701 in KMMainWidget::slotMsgSelected(KMMessage*) ()
   from /usr/local/lib/libkmailprivate.so
#25 0x00fbfe29 in KMMainWidget::qt_invoke(int, QUObject*) ()
   from /usr/local/lib/libkmailprivate.so
#26 0x0fe463de in QObject::activate_signal(QConnectionList*, QUObject*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#27 0x00e7657a in KMHeaders::selected(KMMessage*) ()
   from /usr/local/lib/libkmailprivate.so
#28 0x00e6fa98 in KMHeaders::highlightMessage(QListViewItem*, bool) ()
   from /usr/local/lib/libkmailprivate.so
#29 0x00e6e010 in KMHeaders::finalizeMove(KMail::HeaderItem*, int, int) ()
   from /usr/local/lib/libkmailprivate.so
#30 0x00e6dd98 in KMHeaders::deleteMsg() ()
   from /usr/local/lib/libkmailprivate.so
#31 0x00fc77b0 in KMMainWidget::slotTrashMsg() ()
   from /usr/local/lib/libkmailprivate.so
#32 0x00fbfd8c in KMMainWidget::qt_invoke(int, QUObject*) ()
   from /usr/local/lib/libkmailprivate.so
#33 0x0fe463de in QObject::activate_signal(QConnectionList*, QUObject*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#34 0x0fe4620d in QObject::activate_signal(int) ()
   from /usr/local/lib/libqt-mt.so.30.1
#35 0x0acc11a8 in KAction::activated() () from /usr/local/lib/libkdeui.so.7.0
#36 0x0acc0a2d in KAction::slotActivated() ()
   from /usr/local/lib/libkdeui.so.7.0
#37 0x0acc144f in KAction::qt_invoke(int, QUObject*) ()
   from /usr/local/lib/libkdeui.so.7.0
#38 0x0fe463de in QObject::activate_signal(QConnectionList*, QUObject*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#39 0x0fe4620d in QObject::activate_signal(int) ()
   from /usr/local/lib/libqt-mt.so.30.1
#40 0x02b84aa8 in KAccelPrivate::menuItemActivated() ()
   from /usr/local/lib/libkdecore.so.7.0
#41 0x02b83827 in KAccelPrivate::emitActivatedSignal(KAccelAction*) ()
   from /usr/local/lib/libkdecore.so.7.0
#42 0x02b8360a in KAccelPrivate::eventFilter(QObject*, QEvent*) ()
   from /usr/local/lib/libkdecore.so.7.0
#43 0x0fe440e8 in QObject::activate_filters(QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#44 0x0fe44036 in QObject::event(QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#45 0x0fe7602e in QWidget::event(QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#46 0x0ff2543f in QMainWindow::event(QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#47 0x0fdf2271 in QApplication::internalNotify(QObject*, QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#48 0x0fdf1b91 in QApplication::notify(QObject*, QEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#49 0x02b05666 in KApplication::notify(QObject*, QEvent*) ()
   from /usr/local/lib/libkdecore.so.7.0
#50 0x02b82830 in KAccelEventHandler::x11Event(_XEvent*) ()
   from /usr/local/lib/libkdecore.so.7.0
#51 0x02b0b201 in KApplication::x11EventFilter(_XEvent*) ()
   from /usr/local/lib/libkdecore.so.7.0
#52 0x0fd85ddb in qt_x11EventFilter(_XEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#53 0x0fd8eed7 in QApplication::x11ProcessEvent(_XEvent*) ()
   from /usr/local/lib/libqt-mt.so.30.1
#54 0x0fda495d in QEventLoop::processEvents(unsigned) ()
   from /usr/local/lib/libqt-mt.so.30.1
#55 0x0fe0207b in QEventLoop::enterLoop() ()
   from /usr/local/lib/libqt-mt.so.30.1
#56 0x0fe01f40 in QEventLoop::exec() () from /usr/local/lib/libqt-mt.so.30.1
#57 0x0fdf246c in QApplication::exec() () from /usr/local/lib/libqt-mt.so.30.1
#58 0x1c0108c1 in __register_frame_info ()
#59 0x1c010080 in ?? ()
#60 0x00000001 in ?? ()
#61 0xcf7fd464 in ?? ()
#62 0xcf7fd46c in ?? ()
#63 0x1c010011 in ?? ()
#64 0xcf7fd5cc in ?? ()
#65 0xcf7fd440 in ?? ()
#66 0x1c00d2f5 in ?? ()
#67 0x1c01006e in ?? ()
#68 0x00000000 in ?? ()