Version:           1.11.3 (using 4.2.3 (KDE 4.2.3), Kubuntu packages)
Compiler:          cc
OS:                Linux (i686) release 2.6.28-12-generic

It happened when moving an e-mail into another folder.:

Application: KMail (kmail), signal SIGABRT
[Current thread is 0 (LWP 6509)]

Thread 2 (Thread 0xb18c0b90 (LWP 7625)):
#0  0xb801d430 in __kernel_vsyscall ()
#1  0xb5c447b1 in select () from /lib/tls/i686/cmov/libc.so.6
#2  0xb5f18380 in QProcessManager::run (this=0x898ab30) at io/qprocess_unix.cpp:305
#3  0xb5e4696e in QThreadPrivate::start (arg=0x898ab30) at thread/qthread_unix.cpp:189
#4  0xb50784ff in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#5  0xb5c4c49e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb3c6eb40 (LWP 6509)):
[KCrash Handler]
#6  0xb801d430 in __kernel_vsyscall ()
#7  0xb5b936d0 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb5b95098 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb5e3e595 in qt_message_output (msgType=QtFatalMsg, buf=0xaf405e0 "ASSERT: \"!transferInProgress( serNum )\" in file /build/buildd/kdepim-4.2.3/kmail/messageproperty.cpp, line 180")
    at global/qglobal.cpp:2006
#10 0xb5e3e681 in qFatal (msg=0xb5f8d318 "ASSERT: \"%s\" in file %s, line %d") at global/qglobal.cpp:2201
#11 0xb5e3e775 in qt_assert (assertion=0xb78ecc6b "!transferInProgress( serNum )", file=0xb78ecc18 "/build/buildd/kdepim-4.2.3/kmail/messageproperty.cpp", line=180) at global/qglobal.cpp:1777
#12 0xb741dcf0 in KMail::MessageProperty::forget (msgBase=0xb6b61f8) at /build/buildd/kdepim-4.2.3/kmail/messageproperty.cpp:180
#13 0xb74827da in ~KMMsgBase (this=0xb6b61f8) at /build/buildd/kdepim-4.2.3/kmail/kmmsgbase.cpp:125
#14 0xb72e1624 in ~KMMessage (this=0xb6b61f8) at /build/buildd/kdepim-4.2.3/kmail/kmmessage.cpp:225
#15 0xb73f17a2 in ~KMReaderWin (this=0xb53ef98) at /build/buildd/kdepim-4.2.3/kmail/kmreaderwin.cpp:909
#16 0xb5f49e3f in QObjectPrivate::deleteChildren (this=0xb537e80) at kernel/qobject.cpp:1854
#17 0xb623966b in ~QWidget (this=0xb52ff78) at kernel/qwidget.cpp:1373
#18 0xb6635531 in ~QMainWindow (this=0xb52ff78) at widgets/qmainwindow.cpp:328
#19 0xb7f2987b in ~KMainWindow (this=0xb52ff78) at /build/buildd/kde4libs-4.2.3/kdeui/widgets/kmainwindow.cpp:467
#20 0xb7f6c9a7 in ~KXmlGuiWindow (this=0xb52ff78, __vtt_parm=0xb7a52f98) at /build/buildd/kde4libs-4.2.3/kdeui/xmlgui/kxmlguiwindow.cpp:127
#21 0xb7686878 in ~SecondaryWindow (this=0xb52ff78, __vtt_parm=0xb7a52f94) at /build/buildd/kdepim-4.2.3/kmail/secondarywindow.cpp:56
#22 0xb75f06ea in ~KMReaderMainWin (this=0xb52ff78) at /build/buildd/kdepim-4.2.3/kmail/kmreadermainwin.cpp:117
#23 0xb5f49b25 in qDeleteInEventHandler (o=0x6) at kernel/qobject.cpp:3771
#24 0xb5f4b3cb in QObject::event (this=0xb52ff78, e=0xb006e58) at kernel/qobject.cpp:1101
#25 0xb623e440 in QWidget::event (this=0xb52ff78, event=0xb006e58) at kernel/qwidget.cpp:7913
#26 0xb66360d7 in QMainWindow::event (this=0xb52ff78, event=0xb006e58) at widgets/qmainwindow.cpp:1396
#27 0xb7f28a67 in KMainWindow::event (this=0xb52ff78, ev=0xb006e58) at /build/buildd/kde4libs-4.2.3/kdeui/widgets/kmainwindow.cpp:1094
#28 0xb7f6d84c in KXmlGuiWindow::event (this=0xb52ff78, ev=0xb006e58) at /build/buildd/kde4libs-4.2.3/kdeui/xmlgui/kxmlguiwindow.cpp:131
#29 0xb61e7e9c in QApplicationPrivate::notify_helper (this=0x88f76b0, receiver=0xb52ff78, e=0xb006e58) at kernel/qapplication.cpp:4084
#30 0xb61f0282 in QApplication::notify (this=0xbf839738, receiver=0xb52ff78, e=0xb006e58) at kernel/qapplication.cpp:4049
#31 0xb7e44e5d in KApplication::notify (this=0xbf839738, receiver=0xb52ff78, event=0xb006e58) at /build/buildd/kde4libs-4.2.3/kdeui/kernel/kapplication.cpp:307
#32 0xb5f3aa3b in QCoreApplication::notifyInternal (this=0xbf839738, receiver=0xb52ff78, event=0xb006e58) at kernel/qcoreapplication.cpp:602
#33 0xb5f3b695 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x88d11f0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#34 0xb5f3b88d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1132
#35 0xb5f667ef in postEventSourceDispatch (s=0x88ff740) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#36 0xb436fb88 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#37 0xb43730eb in ?? () from /usr/lib/libglib-2.0.so.0
#38 0xb4373268 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#39 0xb5f66438 in QEventDispatcherGlib::processEvents (this=0x88dc5a8, flags={i = -1081895528}) at kernel/qeventdispatcher_glib.cpp:323
#40 0xb6289365 in QGuiEventDispatcherGlib::processEvents (this=0x88dc5a8, flags={i = -1081895480}) at kernel/qguieventdispatcher_glib.cpp:202
#41 0xb5f3906a in QEventLoop::processEvents (this=0xbf839640, flags={i = -1081895416}) at kernel/qeventloop.cpp:149
#42 0xb5f394aa in QEventLoop::exec (this=0xbf839640, flags={i = -1081895352}) at kernel/qeventloop.cpp:200
#43 0xb5f3b959 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#44 0xb61e7d17 in QApplication::exec () at kernel/qapplication.cpp:3553
#45 0x0804a7a0 in main (argc=) at /build/buildd/kdepim-4.2.3/kmail/main.cpp:146