Application that crashed: kmail
Version of the application: 1.12.4
KDE Version: 4.3.4 (KDE 4.3.4)
Qt Version: 4.5.3
Operating System: Linux 2.6.32-3.slh.3-sidux-686 i686
Distribution: Debian GNU/Linux unstable (sid)

What I was doing when the application crashed:
Actually, I searched for a while, then I opened two messages matching (double click). When opening the 3rd one, kmail crashed.

 -- Backtrace:
Application: KMail (kmail), signal: Segmentation fault
[KCrash Handler]
#6  QString (this=0x10d42d18, s=..., number=false) at ../../include/QtCore/../../src/corelib/tools/qstring.h:711
#7  QTextStreamPrivate::putString (this=0x10d42d18, s=..., number=false) at io/qtextstream.cpp:933
#8  0xb68adb4b in QTextStream::operator<< (this=0xaa89808, string=...) at io/qtextstream.cpp:2511
#9  0xb705c498 in ?? () from /usr/lib/libkmailprivate.so.4
#10 0xb7005df4 in ?? () from /usr/lib/libkmailprivate.so.4
#11 0xb6ffc29b in ?? () from /usr/lib/libkmailprivate.so.4
#12 0xb6e9e90a in KMMainWidget::slotSelectMessage(KMMessage*) () from /usr/lib/libkmailprivate.so.4
#13 0xb6dfea13 in ?? () from /usr/lib/libkmailprivate.so.4
#14 0xb6dfef4e in ?? () from /usr/lib/libkmailprivate.so.4
#15 0xb691b303 in QMetaObject::activate (sender=0xbcac388, from_signal_index=96, to_signal_index=96, argv=0xbf855028) at kernel/qobject.cpp:3112
#16 0xb691bf42 in QMetaObject::activate (sender=0xbcac388, m=0xb67aacb0, local_signal_index=1, argv=0xbf855028) at kernel/qobject.cpp:3186
#17 0xb64fe5a9 in QTreeWidget::itemClicked (this=0xbcac388, _t1=0xdaa2298, _t2=0) at .moc/release-shared/moc_qtreewidget.cpp:201
#18 0xb65028d5 in QTreeWidgetPrivate::_q_emitItemClicked (this=0xcb2a7a8, index=...) at itemviews/qtreewidget.cpp:2228
#19 0xb650bc69 in QTreeWidget::qt_metacall (this=0xbcac388, _c=QMetaObject::InvokeMetaMethod, _id=16, _a=0xbf85519c) at .moc/release-shared/moc_qtreewidget.cpp:144
#20 0xb6dfd01a in ?? () from /usr/lib/libkmailprivate.so.4
#21 0xb691b303 in QMetaObject::activate (sender=0xbcac388, from_signal_index=32, to_signal_index=32, argv=0xbf85519c) at kernel/qobject.cpp:3112
#22 0xb691bf42 in QMetaObject::activate (sender=0xbcac388, m=0xb67a9c04, local_signal_index=1, argv=0xbf85519c) at kernel/qobject.cpp:3186
#23 0xb6480253 in QAbstractItemView::clicked (this=0xbcac388, _t1=...) at .moc/release-shared/moc_qabstractitemview.cpp:321
#24 0xb648dc15 in QAbstractItemView::mouseReleaseEvent (this=0xbcac388, event=0xbf855b7c) at itemviews/qabstractitemview.cpp:1660
#25 0xb64d0e7c in QTreeView::mouseReleaseEvent (this=0xbcac388, event=0xbf855b7c) at itemviews/qtreeview.cpp:1796
#26 0xb5f9b9fb in QWidget::event (this=0xbcac388, event=0xbf855b7c) at kernel/qwidget.cpp:7554
#27 0xb6341543 in QFrame::event (this=0xbcac388, e=0xbf855b7c) at widgets/qframe.cpp:559
#28 0xb63df59f in QAbstractScrollArea::viewportEvent (this=0xbcac388, e=0x2c) at widgets/qabstractscrollarea.cpp:962
#29 0xb6490887 in QAbstractItemView::viewportEvent (this=0xbcac388, event=0xbf855b7c) at itemviews/qabstractitemview.cpp:1476
#30 0xb64cb696 in QTreeView::viewportEvent (this=0xbcac388, event=0xbf855b7c) at itemviews/qtreeview.cpp:1266
#31 0xb63e1b75 in QAbstractScrollAreaPrivate::viewportEvent (this=0x988d058, o=0xd5cd230, e=0xbf855b7c) at widgets/qabstractscrollarea_p.h:100
#32 QAbstractScrollAreaFilter::eventFilter (this=0x988d058, o=0xd5cd230, e=0xbf855b7c) at widgets/qabstractscrollarea_p.h:111
#33 0xb690541a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x85a3668, receiver=0xd5cd230, event=0xbf855b7c) at kernel/qcoreapplication.cpp:726
#34 0xb5f45a6c in QApplicationPrivate::notify_helper (this=0x85a3668, receiver=0xd5cd230, e=0xbf855b7c) at kernel/qapplication.cpp:4061
#35 0xb5f4e551 in QApplication::notify (this=0xbf8574e0, receiver=0xd5cd230, e=0xbf855b7c) at kernel/qapplication.cpp:3767
#36 0xb76ca62d in KApplication::notify (this=0xbf8574e0, receiver=0xd5cd230, event=0xbf855b7c) at ../../kdeui/kernel/kapplication.cpp:302
#37 0xb69061eb in QCoreApplication::notifyInternal (this=0xbf8574e0, receiver=0xd5cd230, event=0xbf855b7c) at kernel/qcoreapplication.cpp:610
#38 0xb5f4d5de in QCoreApplication::sendSpontaneousEvent (receiver=0xd5cd230, event=0xbf855b7c, alienWidget=0xd5cd230, nativeWidget=0x9b55f60, buttonDown=0xb67bc580, lastMouseReceiver=...)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:216
#39 QApplicationPrivate::sendMouseEvent (receiver=0xd5cd230, event=0xbf855b7c, alienWidget=0xd5cd230, nativeWidget=0x9b55f60, buttonDown=0xb67bc580, lastMouseReceiver=...)
    at kernel/qapplication.cpp:2924
#40 0xb5fbc175 in QETWidget::translateMouseEvent (this=0x9b55f60, event=0xbf85712c) at kernel/qapplication_x11.cpp:4411
#41 0xb5fbb646 in QApplication::x11ProcessEvent (this=0xbf8574e0, event=0xbf85712c) at kernel/qapplication_x11.cpp:3430
#42 0xb5fe5bc2 in x11EventSourceDispatch (s=0x85a6db0, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#43 0xb40182e5 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#44 0xb401c000 in ?? () from /lib/libglib-2.0.so.0
#45 0xb401c198 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#46 0xb6931041 in QEventDispatcherGlib::processEvents (this=0x857d2b8, flags=...) at kernel/qeventdispatcher_glib.cpp:407
#47 0xb5fe5305 in QGuiEventDispatcherGlib::processEvents (this=0x857d2b8, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#48 0xb690483a in QEventLoop::processEvents (this=0xbf8573e0, flags=...) at kernel/qeventloop.cpp:149
#49 0xb6904c82 in QEventLoop::exec (this=0xbf8573e0, flags=...) at kernel/qeventloop.cpp:201
#50 0xb69070d9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#51 0xb5f45917 in QApplication::exec () at kernel/qapplication.cpp:3525
#52 0x0804a6e2 in _start ()

Reported using DrKonqi