Version:            (using KDE 4.2.0)
Installed from:    Ubuntu Packages

1) I open Kontact
2) I open Summary page
3) I click on some ToDo item.
4) Often, Kontact crashes with following stacktrace:

Application: Kontact (kontact), signal SIGSEGV
[Current thread is 0 (LWP 3599)]

Thread 2 (Thread 0xb18fab90 (LWP 3606)):
#0  0xb7f65430 in __kernel_vsyscall ()
#1  0xb59dddf1 in select () from /lib/tls/i686/cmov/libc.so.6
#2  0xb5cac150 in ?? () from /usr/lib/libQtCore.so.4
#3  0xb5bdc6ae in ?? () from /usr/lib/libQtCore.so.4
#4  0xb531350f in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#5  0xb59e5a0e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb4a8e6c0 (LWP 3599)):
[KCrash Handler]
#6  0xb5bfdb26 in qHash () from /usr/lib/libQtCore.so.4
#7  0xb7290fbf in QHash<QString, KCal::Event*>::findNode (this=0x9656128, akey=@0x9db4080, ahp=0x0) at /usr/include/qt4/QtCore/qhash.h:854
#8  0xb728be4a in KCal::CalendarLocal::event (this=0x9655698, uid=@0x9db4080) at /usr/include/qt4/QtCore/qhash.h:588
#9  0xb72dd767 in KCal::ResourceCached::event (this=0x9655ef0, uid=@0x9db4080) at /build/buildd/kdepimlibs-4.2.0/kcal/resourcecached.cpp:253
#10 0xb72ebe42 in KCal::CalendarResources::event (this=0x9648528, uid=@0x9db4080) at /build/buildd/kdepimlibs-4.2.0/kcal/calendarresources.cpp:468
#11 0xb728362e in KCal::Calendar::incidence (this=0x9648528, uid=@0x9db4080) at /build/buildd/kdepimlibs-4.2.0/kcal/calendar.cpp:521
#12 0xaf83724c in CalendarView::editIncidence (this=0x9679e80, uid=@0x9db4080) at /build/buildd/kdepim-4.2.0/korganizer/calendarview.cpp:1892
#13 0xaf8a8547 in ActionManager::editIncidence (this=0x9906e20, uid=@0x9db4080) at /build/buildd/kdepim-4.2.0/korganizer/actionmanager.cpp:1456
#14 0xaf8cb917 in KOrganizerIfaceImpl::editIncidence (this=0x9650e68, uid=@0x9db4080) at /build/buildd/kdepim-4.2.0/korganizer/korganizerifaceimpl.cpp:91
#15 0xaf909d28 in KorganizerAdaptor::qt_metacall (this=0x9607848, _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0xbff63758)
    at /build/buildd/kdepim-4.2.0/obj-i486-linux-gnu/korganizer/korganizeradaptor.cpp:63
#16 0xb5dd526e in ?? () from /usr/lib/libQtDBus.so.4
#17 0xb5dd64a7 in ?? () from /usr/lib/libQtDBus.so.4
#18 0xb5dd69b1 in ?? () from /usr/lib/libQtDBus.so.4
#19 0xb5dd7527 in ?? () from /usr/lib/libQtDBus.so.4
#20 0xb5dd7b4a in ?? () from /usr/lib/libQtDBus.so.4
#21 0xb5dd7e09 in ?? () from /usr/lib/libQtDBus.so.4
#22 0xb5dd9b9f in ?? () from /usr/lib/libQtDBus.so.4
#23 0xb5dc3a31 in QDBusConnection::call () from /usr/lib/libQtDBus.so.4
#24 0xb5de2dab in QDBusAbstractInterface::callWithArgumentList () from /usr/lib/libQtDBus.so.4
#25 0xb1aefa59 in TodoSummaryWidget::viewTodo (this=0x967b548, uid=@0x999aeb4) at /build/buildd/kdepim-4.2.0/obj-i486-linux-gnu/kontact/plugins/korganizer/korganizerinterface.h:70
#26 0xb1af2cd5 in TodoSummaryWidget::qt_metacall (this=0x967b548, _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0xbff63f7c)
    at /build/buildd/kdepim-4.2.0/obj-i486-linux-gnu/kontact/plugins/korganizer/todosummarywidget.moc:80
#27 0xb5ce1a60 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#28 0xb5ce27e2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#29 0xb6db5803 in KUrlLabel::leftClickedUrl (this=0x98903c8, _t1=@0x999aeb4) at /build/buildd/kde4libs-4.2.0/obj-i486-linux-gnu/kdeui/kurllabel.moc:228
#30 0xb6db6642 in KUrlLabel::mouseReleaseEvent (this=0x98903c8, event=0xbff64598) at /build/buildd/kde4libs-4.2.0/kdeui/widgets/kurllabel.cpp:121
#31 0xb61d6962 in QWidget::event () from /usr/lib/libQtGui.so.4
#32 0xb650dfd3 in QFrame::event () from /usr/lib/libQtGui.so.4
#33 0xb6513579 in QLabel::event () from /usr/lib/libQtGui.so.4
#34 0xb6db6137 in KUrlLabel::event (this=0x98903c8, event=0xbff64598) at /build/buildd/kde4libs-4.2.0/kdeui/widgets/kurllabel.cpp:329
#35 0xb617e8ec in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#36 0xb61870e1 in QApplication::notify () from /usr/lib/libQtGui.so.4
#37 0xb6c97fed in KApplication::notify (this=0xbff64e68, receiver=0x98903c8, event=0xbff64598) at /build/buildd/kde4libs-4.2.0/kdeui/kernel/kapplication.cpp:307
#38 0xb5ccce61 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#39 0xb618636e in QApplicationPrivate::sendMouseEvent () from /usr/lib/libQtGui.so.4
#40 0xb61f0656 in ?? () from /usr/lib/libQtGui.so.4
#41 0xb61ef9e5 in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#42 0xb62197aa in ?? () from /usr/lib/libQtGui.so.4
#43 0xb4fa56f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#44 0xb4fa8da3 in ?? () from /usr/lib/libglib-2.0.so.0
#45 0xb4fa8f61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#46 0xb5cf7478 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#47 0xb6218ea5 in ?? () from /usr/lib/libQtGui.so.4
#48 0xb5ccb52a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#49 0xb5ccb6ea in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#50 0xb5ccdda5 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#51 0xb617e767 in QApplication::exec () from /usr/lib/libQtGui.so.4
#52 0x0804c072 in main (argc=1, argv=0xbff65164) at /build/buildd/kdepim-4.2.0/kontact/src/main.cpp:218