Application that crashed: kmail
Version of the application: 1.12.0
KDE Version: 4.2.96 (KDE 4.2.96 (KDE 4.3 RC2))
Qt Version: 4.5.2
Operating System: Linux 2.6.30-gentoo-r2 x86_64

What I was doing when the application crashed:
This happen just first time, so I can't say if it will be reproducible.
It crashed when I closed program using keyboard shortcut [ctrl]-Q

 -- Backtrace:
Application: KMail (kmail), signal: Aborted
[Current thread is 0 (LWP 8993)]

Thread 2 (Thread 0x7fa4304d2950 (LWP 22991)):
#0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:91
#1  0x00007fa4496b98be in _L_lock_3849 () from /lib/libc.so.6
#2  0x00007fa4496b5f9b in *__GI___libc_free (mem=0x7fa449991a00) at malloc.c:3623
#3  0x00007fa441e381da in ?? () from /usr/lib/libglib-2.0.so.0
#4  0x00007fa44a011722 in ~QEventDispatcherGlib (this=0x29ed030) at kernel/qeventdispatcher_glib.cpp:289
#5  0x00007fa449f1689f in QThreadPrivate::finish (arg=<value optimized out>) at thread/qthread_unix.cpp:212
#6  0x00007fa449f169c6 in QThreadPrivate::start (arg=0x18e37b0) at thread/qthread_unix.cpp:190
#7  0x00007fa4491e0017 in start_thread (arg=<value optimized out>) at pthread_create.c:297
#8  0x00007fa44971148d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#9  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7fa44c70d770 (LWP 8993)):
[KCrash Handler]
#5  0x00007fa449673205 in *__GI_raise (sig=<value optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#6  0x00007fa449674723 in *__GI_abort () at abort.c:88
#7  0x00007fa4496aecf8 in __libc_message (do_abort=2, fmt=0x7fa44975fef8 "*** glibc detected *** %s: %s: 0x%s ***\n") at ../sysdeps/unix/sysv/linux/libc_fatal.c:170
#8  0x00007fa4496b4468 in malloc_printerr (action=2, str=0x7fa44975d52d "free(): invalid pointer", ptr=<value optimized out>) at malloc.c:5994
#9  0x00007fa4496b5fa6 in *__GI___libc_free (mem=0x7fa4497567a0) at malloc.c:3625
#10 0x00007fa449ff8e30 in QObjectPrivate::derefSender (this=0x21919e0, sender=0x20370c0, signal=7) at ../../include/QtCore/../../src/corelib/tools/qlist.h:348
#11 0x00007fa44a000086 in QMetaObject::disconnect (sender=0x20370c0, signal_index=7, receiver=0x214bf80, method_index=-1) at kernel/qobject.cpp:2856
#12 0x00007fa44a0006ab in QObject::disconnect (sender=0x20370c0, signal=0x0, receiver=0x214bf80, method=0x0) at kernel/qobject.cpp:2675
#13 0x00007fa44a7f6793 in QMenu::actionEvent (this=0x214bf80, e=0x7fff545ad190) at ../../include/QtCore/../../src/corelib/kernel/qobject.h:222
#14 0x00007fa44a4b5b6a in QWidget::event (this=0x214bf80, event=0x7fff545ad190) at kernel/qwidget.cpp:7906
#15 0x00007fa44a7fa6ab in QMenu::event (this=0x214bf80, e=0x7fff545ad190) at widgets/qmenu.cpp:2353
#16 0x00007fa44a467f1d in QApplicationPrivate::notify_helper (this=0x18e5560, receiver=0x214bf80, e=0x7fff545ad190) at kernel/qapplication.cpp:4056
#17 0x00007fa44a47097a in QApplication::notify (this=0x7fff545ae360, receiver=0x214bf80, e=0x7fff545ad190) at kernel/qapplication.cpp:4021
#18 0x00007fa44c15853b in KApplication::notify (this=0x7fff545ae360, receiver=0x214bf80, event=0x7fff545ad190)
    at /var/tmp/portage/kde-base/kdelibs-4.2.96/work/kdelibs-4.2.96/kdeui/kernel/kapplication.cpp:302
#19 0x00007fa449feb8cc in QCoreApplication::notifyInternal (this=0x7fff545ae360, receiver=0x214bf80, event=0x7fff545ad190) at kernel/qcoreapplication.cpp:606
#20 0x00007fa44a4a8681 in QWidget::removeAction (this=0x214bf80, action=0x20370c0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#21 0x00007fa44a4649a4 in ~QAction (this=0x20370c0) at kernel/qaction.cpp:605
#22 0x00007fa44a4bac12 in ~QWidgetAction (this=0x20370c0) at kernel/qwidgetaction.cpp:130
#23 0x00007fa44c086ef1 in ~KActionMenu (this=0x20370c0) at /var/tmp/portage/kde-base/kdelibs-4.2.96/work/kdelibs-4.2.96/kdeui/actions/kactionmenu.cpp:78
#24 0x00007fa449ff8c79 in QObjectPrivate::deleteChildren (this=0x2031b30) at kernel/qobject.cpp:1838
#25 0x00007fa449fff6d1 in ~QObject (this=0x2031a70) at kernel/qobject.cpp:836
#26 0x00007fa44b5b9b55 in ~MessageActions (this=0x2031a70) at /var/tmp/portage/kde-base/kmail-4.2.96/work/kmail-4.2.96/kmail/messageactions.h:41
#27 0x00007fa449ff8c79 in QObjectPrivate::deleteChildren (this=0x1d13ec0) at kernel/qobject.cpp:1838
#28 0x00007fa44a4adacd in ~QWidget (this=0x1cbebe0) at kernel/qwidget.cpp:1367
#29 0x00007fa44b485161 in ~KMMainWidget (this=0x1cbebe0) at /var/tmp/portage/kde-base/kmail-4.2.96/work/kmail-4.2.96/kmail/kmmainwidget.cpp:289
#30 0x00007fa449ff8c79 in QObjectPrivate::deleteChildren (this=0x1c7e3c0) at kernel/qobject.cpp:1838
#31 0x00007fa44a4adacd in ~QWidget (this=0x1b1bb30) at kernel/qwidget.cpp:1367
#32 0x00007fa44c228ef9 in ~KMainWindow (this=0x1b1bb30) at /var/tmp/portage/kde-base/kdelibs-4.2.96/work/kdelibs-4.2.96/kdeui/widgets/kmainwindow.cpp:467
#33 0x00007fa44b1ddc78 in ~KMMainWin (this=0x1b1bb30) at /var/tmp/portage/kde-base/kmail-4.2.96/work/kmail-4.2.96/kmail/kmmainwin.cpp:106
#34 0x00007fa449ffa695 in QObject::event (this=0x1b1bb30, e=0x2321) at kernel/qobject.cpp:1085
#35 0x00007fa44a4b516c in QWidget::event (this=0x1b1bb30, event=0x2b7c560) at kernel/qwidget.cpp:7946
#36 0x00007fa44a7d30eb in QMainWindow::event (this=0x1b1bb30, event=0x2b7c560) at widgets/qmainwindow.cpp:1399
#37 0x00007fa44c264c88 in KXmlGuiWindow::event (this=0x2321, ev=0x2321) at /var/tmp/portage/kde-base/kdelibs-4.2.96/work/kdelibs-4.2.96/kdeui/xmlgui/kxmlguiwindow.cpp:131
#38 0x00007fa44a467f1d in QApplicationPrivate::notify_helper (this=0x18e5560, receiver=0x1b1bb30, e=0x2b7c560) at kernel/qapplication.cpp:4056
#39 0x00007fa44a47097a in QApplication::notify (this=0x7fff545ae360, receiver=0x1b1bb30, e=0x2b7c560) at kernel/qapplication.cpp:4021
#40 0x00007fa44c15853b in KApplication::notify (this=0x7fff545ae360, receiver=0x1b1bb30, event=0x2b7c560)
    at /var/tmp/portage/kde-base/kdelibs-4.2.96/work/kdelibs-4.2.96/kdeui/kernel/kapplication.cpp:302
#41 0x00007fa449feb8cc in QCoreApplication::notifyInternal (this=0x7fff545ae360, receiver=0x1b1bb30, event=0x2b7c560) at kernel/qcoreapplication.cpp:606
#42 0x00007fa449fec227 in QCoreApplicationPrivate::sendPostedEvents (receiver=<value optimized out>, event_type=0, data=0x18b1340)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#43 0x00007fa44a010fb3 in postEventSourceDispatch (s=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#44 0x00007fa441e388d1 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#45 0x00007fa441e3bfa0 in ?? () from /usr/lib/libglib-2.0.so.0
#46 0x00007fa441e3c13c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#47 0x00007fa44a010c4f in QEventDispatcherGlib::processEvents (this=0x18b0fa0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#48 0x00007fa44a4ee90f in QGuiEventDispatcherGlib::processEvents (this=0x2321, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#49 0x00007fa449fea272 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 1415242096}) at kernel/qeventloop.cpp:149
#50 0x00007fa449fea40c in QEventLoop::exec (this=0x7fff545ae1b0, flags={i = 1415242176}) at kernel/qeventloop.cpp:197
#51 0x00007fa449fec4cc in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#52 0x000000000040305b in main (argc=<value optimized out>, argv=<value optimized out>) at /var/tmp/portage/kde-base/kmail-4.2.96/work/kmail-4.2.96/kmail/main.cpp:146

Reported using DrKonqi