Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.3.00 (KDE 4.3.0) "release 155"
Qt Version: 4.5.2
Operating System: Linux 2.6.27.25-0.1-default i686

What I was doing when the application crashed:
I added the Lancelot widget to my desktop, then I clicked it. It displayed a window and then Plasma crashed.

 -- Backtrace:
Application: Área de trabajo de Plasma (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0xb5e41700 (LWP 9349))]

Thread 3 (Thread 0xa9172b90 (LWP 9352)):
#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb7cc5c35 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb7d25582 in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQtCore.so.4
#3  0xb759aad2 in ?? () from /usr/lib/libQtNetwork.so.4
#4  0xb7d24572 in ?? () from /usr/lib/libQtCore.so.4
#5  0xb7cc21b5 in start_thread () from /lib/libpthread.so.0
#6  0xb65093be in clone () from /lib/libc.so.6

Thread 2 (Thread 0xa6819b90 (LWP 9546)):
#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb7cc5f62 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb7d2555c in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQtCore.so.4
#3  0xb7d1ab96 in ?? () from /usr/lib/libQtCore.so.4
#4  0xb7d24572 in ?? () from /usr/lib/libQtCore.so.4
#5  0xb7cc21b5 in start_thread () from /lib/libpthread.so.0
#6  0xb65093be in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb5e41700 (LWP 9349)):
[KCrash Handler]
#6  0xb5bcf1cd in Plasma::ExtenderItem::config() const () from /usr/lib/libplasma.so.3
#7  0xb5bd0de3 in Plasma::ExtenderItem::isGroup() const () from /usr/lib/libplasma.so.3
#8  0xb5bc6faa in Plasma::Extender::isEmpty() const () from /usr/lib/libplasma.so.3
#9  0xb5bc7017 in ?? () from /usr/lib/libplasma.so.3
#10 0xb5bc77d5 in Plasma::Extender::itemAddedEvent(Plasma::ExtenderItem*, QPointF const&) () from /usr/lib/libplasma.so.3
#11 0xb5bc6a47 in ?? () from /usr/lib/libplasma.so.3
#12 0xb5bd1f4f in Plasma::ExtenderItem::setExtender(Plasma::Extender*, QPointF const&) () from /usr/lib/libplasma.so.3
#13 0xb5bd3236 in Plasma::ExtenderItem::ExtenderItem(Plasma::Extender*, unsigned int) () from /usr/lib/libplasma.so.3
#14 0xa9266286 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#15 0xa926bbd7 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#16 0xb7e2e788 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/libQtCore.so.4
#17 0xb7e2f412 in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#18 0xa9247d63 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#19 0xa924900c in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#20 0xb7e2e788 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/libQtCore.so.4
#21 0xb7e2f412 in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#22 0xa9249483 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#23 0xa9258024 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#24 0xa9258ea1 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#25 0xb7e21d49 in QMetaMethod::invoke(QObject*, Qt::ConnectionType, QGenericReturnArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument) const () from /usr/lib/libQtCore.so.4
#26 0xb7e224cf in QMetaObject::invokeMethod(QObject*, char const*, Qt::ConnectionType, QGenericReturnArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument) () from /usr/lib/libQtCore.so.4
#27 0xb5bb9fcd in ?? () from /usr/lib/libplasma.so.3
#28 0xb5bba6fd in Plasma::DataEngine::connectSource(QString const&, QObject*, unsigned int, Plasma::IntervalAlignment) const () from /usr/lib/libplasma.so.3
#29 0xa9256e4b in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#30 0xa9258eba in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#31 0xb7e2e788 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/libQtCore.so.4
#32 0xb7e2f412 in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#33 0xb5bb96f3 in Plasma::DataEngine::sourceAdded(QString const&) () from /usr/lib/libplasma.so.3
#34 0xb5bba9cf in Plasma::DataEngine::setData(QString const&, QHash<QString, QVariant> const&) () from /usr/lib/libplasma.so.3
#35 0xa8582faf in ?? () from /usr/lib/kde4/plasma_engine_notifications.so
#36 0xa8585417 in ?? () from /usr/lib/kde4/plasma_engine_notifications.so
#37 0xb70c3873 in ?? () from /usr/lib/libQtDBus.so.4
#38 0xb70c4939 in ?? () from /usr/lib/libQtDBus.so.4
#39 0xb70c4da1 in ?? () from /usr/lib/libQtDBus.so.4
#40 0xb70c529a in ?? () from /usr/lib/libQtDBus.so.4
#41 0xb7e29970 in QObject::event(QEvent*) () from /usr/lib/libQtCore.so.4
#42 0xb67e07fc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#43 0xb67e8aee in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#44 0xb72d327d in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#45 0xb7e1916b in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#46 0xb7e19db5 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib/libQtCore.so.4
#47 0xb7e19fad in QCoreApplication::sendPostedEvents(QObject*, int) () from /usr/lib/libQtCore.so.4
#48 0xb7e44c8f in ?? () from /usr/lib/libQtCore.so.4
#49 0xb63869c8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#50 0xb638a083 in ?? () from /usr/lib/libglib-2.0.so.0
#51 0xb638a241 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#52 0xb7e448d8 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#53 0xb6880ce5 in ?? () from /usr/lib/libQtGui.so.4
#54 0xb7e1778a in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#55 0xb7e17bd2 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#56 0xb7e1a079 in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#57 0xb67e0677 in QApplication::exec() () from /usr/lib/libQtGui.so.4
#58 0xb486eb30 in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#59 0x0804e505 in _start ()

Reported using DrKonqi