Application that crashed: korganizer
Version of the application: 4.3.0 rc1
KDE Version: 4.2.95 (KDE 4.2.95 (KDE 4.3 RC1))
Qt Version: 4.5.0
Operating System: Linux 2.6.28-13-generic i686
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
STEPS TO REPRODUCE:
On the to-do sidebar, or in the to-do view, click on the "summary" heading.

EXPECT BEHAVIOR:
To-dos are now sorted according to their summary.

ACTUAL BEHAVIOR:
Korganizer crashes.

 -- Backtrace:
Application: KOrganizer (korganizer), signal: Segmentation fault
[KCrash Handler]
#6  0xb77db7e7 in KOTodoModel::rowCount (this=0xbfce390c, parent=@0x8e4c598) at /usr/include/qt4/QtCore/qlist.h:87
#7  0xb6b9a2a7 in QAlgorithmsPrivate::qMerge<int*, int const, QSortFilterProxyModelLessThan> (begin=0x9817020, pivot=0x9817024, end=0x9817028, t=@0x9817020, lessThan=
      {sort_column = -1077003924, source_parent = {r = 149726248, c = -1077003928, p = 0x3, m = 0x1c}, source_model = 0xb619fff4, proxy_model = 0xbfce3978}) at itemviews/qsortfilterproxymodel.cpp:69
#8  0xb6b9a8eb in QAlgorithmsPrivate::qStableSortHelper<int*, int, QSortFilterProxyModelLessThan> (begin=0x9817020, end=0x9817028, t=@0x9817020, lessThan=
      {sort_column = -1077003712, source_parent = {r = 0, c = 149210520, p = 0x8f1fd30, m = 0x5}, source_model = 0x0, proxy_model = 0x981b460})
    at ../../include/QtCore/../../src/corelib/tools/qalgorithms.h:487
#9  0xb6b93a6f in QSortFilterProxyModelPrivate::sort_source_rows (this=0x8f13d58, source_rows=@0x98191f0, source_parent=@0xbfce3a98) at ../../include/QtCore/../../src/corelib/tools/qalgorithms.h:229
#10 0xb6b95e54 in QSortFilterProxyModelPrivate::sort (this=0x8f13d58) at itemviews/qsortfilterproxymodel.cpp:353
#11 0xb77e46ae in KOTodoViewSortFilterProxyModel::sort (this=0x8f1fd30, column=0, order=Qt::AscendingOrder)
    at /build/buildd/kdepim-4.2.95a/korganizer/views/todoview/kotodoviewsortfilterproxymodel.cpp:41
#12 0xb6b3e048 in QTreeViewPrivate::_q_sortIndicatorChanged (this=0x8f50520, column=0, order=Qt::AscendingOrder) at itemviews/qtreeview.cpp:3752
#13 0xb6b51415 in QTreeView::qt_metacall (this=0x8f37e80, _c=QMetaObject::InvokeMetaMethod, _id=24, _a=0xbfce3c18) at .moc/release-shared/moc_qtreeview.cpp:153
#14 0xb77e532a in KOTodoViewView::qt_metacall (this=0x8f37e80, _c=QMetaObject::InvokeMetaMethod, _id=93, _a=0xbfce3c18)
    at /build/buildd/kdepim-4.2.95a/obj-i486-linux-gnu/korganizer/kotodoviewview.moc:62
#15 0xb60c2ca8 in QMetaObject::activate (sender=0x8f01948, from_signal_index=79, to_signal_index=79, argv=0xbfce3c18) at kernel/qobject.cpp:3069
#16 0xb60c3932 in QMetaObject::activate (sender=0x8f01948, m=0xb6e24c1c, local_signal_index=10, argv=0xbfce3c18) at kernel/qobject.cpp:3143
#17 0xb6b11449 in QHeaderView::sortIndicatorChanged (this=0x8f01948, _t1=0, _t2=Qt::AscendingOrder) at .moc/release-shared/moc_qheaderview.cpp:278
#18 0xb6b1bdb1 in QHeaderView::setSortIndicator (this=0x8f01948, logicalIndex=0, order=Qt::AscendingOrder) at itemviews/qheaderview.cpp:1285
#19 0xb6b1be1a in QHeaderViewPrivate::flipSortIndicator (this=0x0, section=0) at itemviews/qheaderview.cpp:3256
#20 0xb6b1db84 in QHeaderView::mouseReleaseEvent (this=0x8f01948, e=0xbfce44e8) at itemviews/qheaderview.cpp:2288
#21 0xb65e3b43 in QWidget::event (this=0x8f01948, event=0xbfce44e8) at kernel/qwidget.cpp:7516
#22 0xb69bd993 in QFrame::event (this=0x8f01948, e=0xbfce44e8) at widgets/qframe.cpp:559
#23 0xb6a5d94f in QAbstractScrollArea::viewportEvent (this=0x8f01948, e=0x0) at widgets/qabstractscrollarea.cpp:962
#24 0xb6b0f647 in QAbstractItemView::viewportEvent (this=0x8f01948, event=0xbfce44e8) at itemviews/qabstractitemview.cpp:1466
#25 0xb6b1a292 in QHeaderView::viewportEvent (this=0x8f01948, e=0xbfce44e8) at itemviews/qheaderview.cpp:2402
#26 0xb6a5ff55 in QAbstractScrollAreaFilter::eventFilter (this=0x8ecc4d8, o=0x8f0bfb0, e=0xbfce44e8) at widgets/qabstractscrollarea_p.h:100
#27 0xb60abc5a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x8d36d88, receiver=0x8f0bfb0, event=0xbfce44e8) at kernel/qcoreapplication.cpp:718
#28 0xb658ce7a in QApplicationPrivate::notify_helper (this=0x8d36d88, receiver=0x8f0bfb0, e=0xbfce44e8) at kernel/qapplication.cpp:4080
#29 0xb6595b11 in QApplication::notify (this=0xbfce4ddc, receiver=0x8f0bfb0, e=0xbfce44e8) at kernel/qapplication.cpp:3786
#30 0xb7ded3dd in KApplication::notify (this=0xbfce4ddc, receiver=0x8f0bfb0, event=0xbfce44e8) at /build/buildd/kde4libs-4.2.95/kdeui/kernel/kapplication.cpp:302
#31 0xb60aca3b in QCoreApplication::notifyInternal (this=0xbfce4ddc, receiver=0x8f0bfb0, event=0xbfce44e8) at kernel/qcoreapplication.cpp:602
#32 0xb6594b7e in QApplicationPrivate::sendMouseEvent (receiver=0x8f0bfb0, event=0xbfce44e8, alienWidget=0x8f0bfb0, nativeWidget=0x8e21870, buttonDown=0xb6e37200, lastMouseReceiver=@0xb6e37204)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:216
#33 0xb660497e in QETWidget::translateMouseEvent (this=0x8e21870, event=0xbfce4b2c) at kernel/qapplication_x11.cpp:4425
#34 0xb6603ca7 in QApplication::x11ProcessEvent (this=0xbfce4ddc, event=0xbfce4b2c) at kernel/qapplication_x11.cpp:3421
#35 0xb662ec6a in x11EventSourceDispatch (s=0x8d3e3b0, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#36 0xb5195b88 in IA__g_main_context_dispatch (context=0x8d3df40) at /build/buildd/glib2.0-2.20.1/glib/gmain.c:1814
#37 0xb51990eb in g_main_context_iterate (context=0x8d3df40, block=1, dispatch=1, self=0x8d36630) at /build/buildd/glib2.0-2.20.1/glib/gmain.c:2448
#38 0xb5199268 in IA__g_main_context_iteration (context=0x8d3df40, may_block=1) at /build/buildd/glib2.0-2.20.1/glib/gmain.c:2511
#39 0xb60d8438 in QEventDispatcherGlib::processEvents (this=0x8d0edb0, flags={i = -1076998936}) at kernel/qeventdispatcher_glib.cpp:323
#40 0xb662e365 in QGuiEventDispatcherGlib::processEvents (this=0x8d0edb0, flags={i = -1076998888}) at kernel/qguieventdispatcher_glib.cpp:202
#41 0xb60ab06a in QEventLoop::processEvents (this=0xbfce4d90, flags={i = -1076998824}) at kernel/qeventloop.cpp:149
#42 0xb60ab4aa in QEventLoop::exec (this=0xbfce4d90, flags={i = -1076998760}) at kernel/qeventloop.cpp:200
#43 0xb60ad959 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#44 0xb658cd17 in QApplication::exec () at kernel/qapplication.cpp:3553
#45 0x0804ec64 in main (argc=) at /build/buildd/kdepim-4.2.95a/korganizer/main.cpp:61

Reported using DrKonqi