Version:            (using KDE 4.1.3)
Compiler:          gcc-4.3.2 
OS:                Linux
Installed from:    Gentoo Packages

Syncing a newly created disconnected IMAP folder for the first time, but seemingly, the host could not be found(?!). Listed the commands (using the up-arrow in the statusbar) and removed the "Connecting to ..." message via the '-' button.

Backtrace:
Application: Kontact (kontact), signal SIGABRT
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0xb4ee06d0 (LWP 8307)]
[New Thread 0xb16a6b90 (LWP 8360)]
[KCrash handler]
#6  0xb7f1e424 in __kernel_vsyscall ()
#7  0xb5318c20 in raise () from /lib/libc.so.6
#8  0xb531a478 in abort () from /lib/libc.so.6
#9  0xb7d26fbd in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbfa35510 "ASSERT: \"!mMailCheckProgressItem\" in file /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/kmacctcachedimap.cpp, line 242")
    at global/qglobal.cpp:2108
#10 0xb7d27086 in qFatal (msg=0xb7e83f9c "ASSERT: \"%s\" in file %s, line %d")
    at global/qglobal.cpp:2309
#11 0xb7d27405 in qt_assert (assertion=0xb22fe2df "!mMailCheckProgressItem", 
    file=0xb2306b1c "/var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/kmacctcachedimap.cpp", line=242) at global/qglobal.cpp:1878
#12 0xb20ac5fa in KMAcctCachedImap::processNewMail (this=0x8b88528, 
    folder=0x8c114b0, recurse=true)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/kmacctcachedimap.cpp:242
#13 0xb20ac854 in KMAcctCachedImap::processNewMail (this=0x8b88528)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/kmacctcachedimap.cpp:207
#14 0xb1f3d3e0 in AccountUpdater::namespacesFetched (this=0x88d4fa0)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/configuredialog.cpp:5434
#15 0xb1f3d455 in AccountUpdater::qt_metacall (this=0x88d4fa0, 
    _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0xbfa37718)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail_build/kmail/configuredialog.moc:133
#16 0xb7e46f39 in QMetaObject::activate (sender=0x8b88528, 
    from_signal_index=<value optimized out>, to_signal_index=10, 
    argv=0xbfa37718) at kernel/qobject.cpp:3028
#17 0xb7e48ee2 in QMetaObject::activate (sender=0x8b88528, m=0xb2419a04, 
    local_signal_index=0, argv=0xbfa37718) at kernel/qobject.cpp:3098
#18 0xb2098259 in KMail::ImapAccountBase::connectionResult (this=0x8b88528, 
    _t1=1, _t2=@0xbfa37758)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail_build/kmail/imapaccountbase.moc:151
#19 0xb20ab120 in KMAcctCachedImap::slotProgressItemCanceled (this=0x8b88528)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/kmacctcachedimap.cpp:453
#20 0xb20ac2f7 in KMAcctCachedImap::qt_metacall (this=0x8b88528, 
    _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0xbfa3786c)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail_build/kmail/kmacctcachedimap.moc:83
#21 0xb7e46f39 in QMetaObject::activate (sender=0x8a81e68, 
    from_signal_index=<value optimized out>, to_signal_index=7, 
    argv=0xbfa3786c) at kernel/qobject.cpp:3028
#22 0xb7e48ee2 in QMetaObject::activate (sender=0x8a81e68, m=0xb6896368, 
    local_signal_index=3, argv=0xbfa3786c) at kernel/qobject.cpp:3098
#23 0xb682b1f3 in KPIM::ProgressItem::progressItemCanceled (this=0x8a81e68, 
    _t1=0x8a81e68)
    at /var/tmp/portage/kde-base/libkdepim-4.1.3/work/libkdepim_build/libkdepim/progressmanager.moc:116
#24 0xb682bb31 in KPIM::ProgressItem::cancel (this=0x8a81e68)
    at /var/tmp/portage/kde-base/libkdepim-4.1.3/work/libkdepim-4.1.3/libkdepim/progressmanager.cpp:101
#25 0xb682d8d4 in KPIM::TransactionItem::slotItemCanceled (this=0x887ebc8)
    at /var/tmp/portage/kde-base/libkdepim-4.1.3/work/libkdepim-4.1.3/libkdepim/progressdialog.cpp:231
#26 0xb682d935 in KPIM::TransactionItem::qt_metacall (this=0x887ebc8, 
    _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0xbfa37a3c)
    at /var/tmp/portage/kde-base/libkdepim-4.1.3/work/libkdepim_build/libkdepim/progressdialog.moc:117
#27 0xb7e46f39 in QMetaObject::activate (sender=0x8cc4758, 
    from_signal_index=<value optimized out>, to_signal_index=30, 
    argv=0xbfa37a3c) at kernel/qobject.cpp:3028
#28 0xb7e47380 in QMetaObject::activate (sender=0x8cc4758, m=0xb60c6364, 
    from_local_signal_index=2, to_local_signal_index=3, argv=0xbfa37a3c)
    at kernel/qobject.cpp:3118
#29 0xb5ef06c1 in QAbstractButton::clicked (this=0x8cc4758, _t1=false)
    at .moc/debug-shared/moc_qabstractbutton.cpp:185
#30 0xb5c1e5b9 in QAbstractButtonPrivate::emitClicked (this=0x8afe438)
    at widgets/qabstractbutton.cpp:544
#31 0xb5c202c4 in QAbstractButtonPrivate::click (this=0x8afe438)
    at widgets/qabstractbutton.cpp:537
#32 0xb5c20546 in QAbstractButton::mouseReleaseEvent (this=0x8cc4758, 
    e=0xbfa380bc) at widgets/qabstractbutton.cpp:1116
#33 0xb590b142 in QWidget::event (this=0x8cc4758, event=0xbfa380bc)
    at kernel/qwidget.cpp:7169
#34 0xb5c1e45e in QAbstractButton::event (this=0x8cc4758, e=0xbfa380bc)
    at widgets/qabstractbutton.cpp:1078
#35 0xb5ccd310 in QPushButton::event (this=0x8cc4758, e=0xbfa380bc)
    at widgets/qpushbutton.cpp:658
#36 0xb58ac94c in QApplicationPrivate::notify_helper (this=0x84311a0, 
    receiver=0x8cc4758, e=0xbfa380bc) at kernel/qapplication.cpp:3809
#37 0xb58b4479 in QApplication::notify (this=0xbfa38728, receiver=0x8cc4758, 
    e=0xbfa380bc) at kernel/qapplication.cpp:3534
#38 0xb79776b1 in KApplication::notify (this=0xbfa38728, receiver=0x8cc4758, 
    event=0xbfa380bc)
    at /var/tmp/portage/kde-base/kdelibs-4.1.3-r1/work/kdelibs-4.1.3/kdeui/kernel/kapplication.cpp:311
#39 0xb7e2eebf in QCoreApplication::notifyInternal (this=0xbfa38728, 
    receiver=0x8cc4758, event=0xbfa380bc) at kernel/qcoreapplication.cpp:593
#40 0xb58b590f in QApplicationPrivate::sendMouseEvent (receiver=0x8cc4758, 
    event=0xbfa380bc, alienWidget=0x8cc4758, nativeWidget=0x84f2cf8, 
    buttonDown=0xb60ccc60, lastMouseReceiver=@0xb60ccc64)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#41 0xb59242f3 in QETWidget::translateMouseEvent (this=0x84f2cf8, 
    event=0xbfa385a8) at kernel/qapplication_x11.cpp:4048
#42 0xb5922c06 in QApplication::x11ProcessEvent (this=0xbfa38728, 
    event=0xbfa385a8) at kernel/qapplication_x11.cpp:3044
#43 0xb594b2f8 in QEventDispatcherX11::processEvents (this=0x842fc08, flags=
      {i = -1079802296}) at kernel/qeventdispatcher_x11.cpp:134
#44 0xb7e2d82a in QEventLoop::processEvents (this=0xbfa386c0, flags=
      {i = -1079802232}) at kernel/qeventloop.cpp:149
#45 0xb7e2d9ea in QEventLoop::exec (this=0xbfa386c0, flags={i = -1079802168})
    at kernel/qeventloop.cpp:200
#46 0xb7e30155 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:851
#47 0xb58ac677 in QApplication::exec () at kernel/qapplication.cpp:3337
#48 0x0804b92d in main (argc=1, argv=0xbfa388e4)
    at /var/tmp/portage/kde-base/kontact-4.1.3/work/kontact-4.1.3/kontact/src/main.cpp:218
#0  0xb7f1e424 in __kernel_vsyscall ()