Application that crashed: kontact
Version of the application: 4.3.5
KDE Version: 4.3.5 (KDE 4.3.5)
Qt Version: 4.6.2
Operating System: Linux 2.6.31-gentoo-r6-yuzuki i686

What I was doing when the application crashed:
Note: A similar crash (probably duplicate) for a previous version was already reported, but the Assistant didn't find any matching reports.

On system start/login, KDE seems to restore multiple instances of Kontact (Error Message appears, asking if I want to start Kontact anyway). If I answer not to start this additional instance, no Kontact is started at all. If I select to start anyway, two instances (windows) are started and crash immediatly with attached backtrace on closing any of the two (using the X-Button on the top right).

This bug has been occuring for several versions before, although it became much less frequent. I can't narrow it down completely, but it occures to me that a system shutdown that was not able to run to completion (system hang up during shutdown, but already outside of X) increases the probability of said bug. When the two instances error appears, the application crashes _always_, though.

Working with one of the windows, not closing the other, has a high risk of crashing the application as well, which will occure within a few minutes of actively using Kmail (not tested with other parts of Kontact).

 -- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault
[KCrash Handler]
#6  0x08407e77 in ?? ()
#7  0xaef2cb4d in Akregator::Feed::unread() const () from /usr/lib/kde4/akregatorpart.so
#8  0xaef36f4f in Akregator::Folder::updateUnreadCount() const () from /usr/lib/kde4/akregatorpart.so
#9  0xaef38d32 in Akregator::Folder::removeChild(Akregator::TreeNode*) () from /usr/lib/kde4/akregatorpart.so
#10 0xaef35030 in Akregator::TreeNode::emitSignalDestroyed() () from /usr/lib/kde4/akregatorpart.so
#11 0xaef2e58a in Akregator::Feed::~Feed() () from /usr/lib/kde4/akregatorpart.so
#12 0xaef35956 in Akregator::Folder::FolderPrivate::~FolderPrivate() () from /usr/lib/kde4/akregatorpart.so
#13 0xaef35a17 in Akregator::Folder::~Folder() () from /usr/lib/kde4/akregatorpart.so
#14 0xaef35956 in Akregator::Folder::FolderPrivate::~FolderPrivate() () from /usr/lib/kde4/akregatorpart.so
#15 0xaef35a17 in Akregator::Folder::~Folder() () from /usr/lib/kde4/akregatorpart.so
#16 0xaef3acf4 in Akregator::FeedList::setRootNode(Akregator::Folder*) () from /usr/lib/kde4/akregatorpart.so
#17 0xaef3d1be in Akregator::FeedList::~FeedList() () from /usr/lib/kde4/akregatorpart.so
#18 0xaef818e8 in boost::detail::sp_counted_impl_p<Akregator::FeedList>::dispose() () from /usr/lib/kde4/akregatorpart.so
#19 0xaef25b30 in Akregator::ArticleDeleteJob::~ArticleDeleteJob() () from /usr/lib/kde4/akregatorpart.so
#20 0xb4ccef2f in QObjectPrivate::deleteChildren() () from /usr/lib/qt4/libQtCore.so.4
#21 0xb4cd6909 in QObject::~QObject() () from /usr/lib/qt4/libQtCore.so.4
#22 0xaeee1fe7 in Akregator::Command::~Command() () from /usr/lib/libakregatorinterfaces.so.4
#23 0xaef61aa9 in Akregator::ExpireItemsCommand::~ExpireItemsCommand() () from /usr/lib/kde4/akregatorpart.so
#24 0xb4ccef2f in QObjectPrivate::deleteChildren() () from /usr/lib/qt4/libQtCore.so.4
#25 0xb5283263 in QWidget::~QWidget() () from /usr/lib/qt4/libQtGui.so.4
#26 0xaef9852c in Akregator::MainWidget::~MainWidget() () from /usr/lib/kde4/akregatorpart.so
#27 0xb6333e4e in ~Part (this=0x86bcde0, __vtt_parm=0xaefe9fa8, __in_chrg=<value optimized out>) at /var/tmp/portage/kde-base/kdelibs-4.3.5/work/kdelibs-4.3.5/kparts/part.cpp:208
#28 0xb633417a in ~ReadOnlyPart (this=0x86bcde0, __vtt_parm=0xaefe9fa4, __in_chrg=<value optimized out>) at /var/tmp/portage/kde-base/kdelibs-4.3.5/work/kdelibs-4.3.5/kparts/part.cpp:459
#29 0xaef95f82 in Akregator::Part::~Part() () from /usr/lib/kde4/akregatorpart.so
#30 0xb71292f9 in Kontact::Plugin::~Plugin() () from /usr/lib/libkontactinterfaces.so.4
#31 0xb0ba5b4c in AkregatorPlugin::~AkregatorPlugin() () from /usr/lib/kde4/kontact_akregatorplugin.so
#32 0xb7148f06 in ~MainWindow (this=0x8148210, __in_chrg=<value optimized out>, __vtt_parm=<value optimized out>)
    at /var/tmp/portage/kde-base/kontact-4.3.5/work/kontact-4.3.5/kontact/src/mainwindow.cpp:274
#33 0xb4cceb55 in qDeleteInEventHandler(QObject*) () from /usr/lib/qt4/libQtCore.so.4
#34 0xb4cd0640 in QObject::event(QEvent*) () from /usr/lib/qt4/libQtCore.so.4
#35 0xb527b3f0 in QWidget::event(QEvent*) () from /usr/lib/qt4/libQtGui.so.4
#36 0xb5680667 in QMainWindow::event(QEvent*) () from /usr/lib/qt4/libQtGui.so.4
#37 0xb5e49777 in KMainWindow::event (this=0x8148210, ev=0x899ade0) at /var/tmp/portage/kde-base/kdelibs-4.3.5/work/kdelibs-4.3.5/kdeui/widgets/kmainwindow.cpp:1101
#38 0xb5e8e08c in KXmlGuiWindow::event (this=0x8148210, ev=0x899ade0) at /var/tmp/portage/kde-base/kdelibs-4.3.5/work/kdelibs-4.3.5/kdeui/xmlgui/kxmlguiwindow.cpp:131
#39 0xb521d84c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/qt4/libQtGui.so.4
#40 0xb5224e87 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/qt4/libQtGui.so.4
#41 0xb5d647ed in KApplication::notify (this=0xbfcaa148, receiver=0x8148210, event=0x899ade0) at /var/tmp/portage/kde-base/kdelibs-4.3.5/work/kdelibs-4.3.5/kdeui/kernel/kapplication.cpp:302
#42 0xb4cbf8ab in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/qt4/libQtCore.so.4
#43 0xb4cc07cf in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib/qt4/libQtCore.so.4
#44 0xb4cc097d in QCoreApplication::sendPostedEvents(QObject*, int) () from /usr/lib/qt4/libQtCore.so.4
#45 0xb4cebb9f in postEventSourceDispatch(_GSource*, int (*)(void*), void*) () from /usr/lib/qt4/libQtCore.so.4
#46 0xb432b425 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#47 0xb432ee78 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#48 0xb432efef in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#49 0xb4ceb6b1 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/qt4/libQtCore.so.4
#50 0xb52d8d95 in QGuiEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/qt4/libQtGui.so.4
#51 0xb4cbdf0a in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/qt4/libQtCore.so.4
#52 0xb4cbe352 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/qt4/libQtCore.so.4
#53 0xb4cc0a49 in QCoreApplication::exec() () from /usr/lib/qt4/libQtCore.so.4
#54 0xb521d8e7 in QApplication::exec() () from /usr/lib/qt4/libQtGui.so.4
#55 0x0804b77b in main (argc=3, argv=0xbfcaa304) at /var/tmp/portage/kde-base/kontact-4.3.5/work/kontact-4.3.5/kontact/src/main.cpp:218

Reported using DrKonqi