I have the same problem.
I use KDE (installed over ubuntu)
Here is my backtrace:

Application: Área de trabajo de Plasma (plasma-desktop), signal: Segmentation fault
[Current thread is 1 (Thread 0xb782b720 (LWP 2948))]

Thread 6 (Thread 0xae6b9b70 (LWP 2950)):
#0  0x0076e7d4 in __pthread_mutex_unlock_usercnt () from /lib/libpthread.so.0
#1  0x001edfa6 in pthread_mutex_unlock () from /lib/libc.so.6
#2  0x046c9870 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#3  0x0851759f in QEventDispatcherGlib::processEvents (this=0xa268b70, flags=...) at kernel/qeventdispatcher_glib.cpp:417
#4  0x084e7609 in QEventLoop::processEvents (this=0xae6b9280, flags=) at kernel/qeventloop.cpp:149
#5  0x084e7a8a in QEventLoop::exec (this=0xae6b9280, flags=...) at kernel/qeventloop.cpp:201
#6  0x083e3b7e in QThread::exec (this=0xa2f7820) at thread/qthread.cpp:490
#7  0x084c635b in QInotifyFileSystemWatcherEngine::run (this=0xa2f7820) at io/qfilesystemwatcher_inotify.cpp:248
#8  0x083e6df9 in QThreadPrivate::start (arg=0xa2f7820) at thread/qthread_unix.cpp:266
#9  0x0076acc9 in start_thread () from /lib/libpthread.so.0
#10 0x001e069e in clone () from /lib/libc.so.6

Thread 5 (Thread 0xad69db70 (LWP 3422)):
#0  0x007b9416 in __kernel_vsyscall ()
#1  0x0076f4dc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0x001edd9d in pthread_cond_wait () from /lib/libc.so.6
#3  0x083e79c7 in wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:88
#4  QWaitCondition::wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:160
#5  0x007ac030 in ThreadWeaver::WeaverImpl::blockThreadUntilJobsAreBeingAssigned (this=0xa690808, th=0xaab5ea8) at ../../../threadweaver/Weaver/WeaverImpl.cpp:365
#6  0x007af7dc in ThreadWeaver::WorkingHardState::waitForAvailableJob (this=0xa6909d0, th=0xaab5ea8) at ../../../threadweaver/Weaver/WorkingHardState.cpp:80
#7  0x007ab55b in ThreadWeaver::WeaverImpl::waitForAvailableJob (this=0xa690808, th=0xaab5ea8) at ../../../threadweaver/Weaver/WeaverImpl.cpp:356
#8  0x007af8d2 in ThreadWeaver::WorkingHardState::applyForWork (this=0xa6909d0, th=0xaab5ea8) at ../../../threadweaver/Weaver/WorkingHardState.cpp:71
#9  0x007ac533 in ThreadWeaver::WeaverImpl::applyForWork (this=0xa690808, th=0xaab5ea8, previous=0x0) at ../../../threadweaver/Weaver/WeaverImpl.cpp:351
#10 0x007af8f1 in ThreadWeaver::WorkingHardState::applyForWork (this=0xa6909d0, th=0xaab5ea8) at ../../../threadweaver/Weaver/WorkingHardState.cpp:74
#11 0x007ac533 in ThreadWeaver::WeaverImpl::applyForWork (this=0xa690808, th=0xaab5ea8, previous=0xa8bd3d0) at ../../../threadweaver/Weaver/WeaverImpl.cpp:351
#12 0x007ad95e in ThreadWeaver::ThreadRunHelper::run (this=0xad69d2e4, parent=0xa690808, th=0xaab5ea8) at ../../../threadweaver/Weaver/Thread.cpp:87
#13 0x007ae07b in ThreadWeaver::Thread::run (this=0xaab5ea8) at ../../../threadweaver/Weaver/Thread.cpp:142
#14 0x083e6df9 in QThreadPrivate::start (arg=0xaab5ea8) at thread/qthread_unix.cpp:266
#15 0x0076acc9 in start_thread () from /lib/libpthread.so.0
#16 0x001e069e in clone () from /lib/libc.so.6

Thread 4 (Thread 0xaff73b70 (LWP 3423)):
#0  0x007b9416 in __kernel_vsyscall ()
#1  0x0076f4dc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0x001edd9d in pthread_cond_wait () from /lib/libc.so.6
#3  0x083e79c7 in wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:88
#4  QWaitCondition::wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:160
#5  0x007ac030 in ThreadWeaver::WeaverImpl::blockThreadUntilJobsAreBeingAssigned (this=0xa690808, th=0xa8f7060) at ../../../threadweaver/Weaver/WeaverImpl.cpp:365
#6  0x007af7dc in ThreadWeaver::WorkingHardState::waitForAvailableJob (this=0xa6909d0, th=0xa8f7060) at ../../../threadweaver/Weaver/WorkingHardState.cpp:80
#7  0x007ab55b in ThreadWeaver::WeaverImpl::waitForAvailableJob (this=0xa690808, th=0xa8f7060) at ../../../threadweaver/Weaver/WeaverImpl.cpp:356
#8  0x007af8d2 in ThreadWeaver::WorkingHardState::applyForWork (this=0xa6909d0, th=0xa8f7060) at ../../../threadweaver/Weaver/WorkingHardState.cpp:71
#9  0x007ac533 in ThreadWeaver::WeaverImpl::applyForWork (this=0xa690808, th=0xa8f7060, previous=0xa6d0938) at ../../../threadweaver/Weaver/WeaverImpl.cpp:351
#10 0x007ad95e in ThreadWeaver::ThreadRunHelper::run (this=0xaff732e4, parent=0xa690808, th=0xa8f7060) at ../../../threadweaver/Weaver/Thread.cpp:87
#11 0x007ae07b in ThreadWeaver::Thread::run (this=0xa8f7060) at ../../../threadweaver/Weaver/Thread.cpp:142
#12 0x083e6df9 in QThreadPrivate::start (arg=0xa8f7060) at thread/qthread_unix.cpp:266
#13 0x0076acc9 in start_thread () from /lib/libpthread.so.0
#14 0x001e069e in clone () from /lib/libc.so.6

Thread 3 (Thread 0xace91b70 (LWP 3424)):
#0  0x007b9416 in __kernel_vsyscall ()
#1  0x0076f4dc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0x001edd9d in pthread_cond_wait () from /lib/libc.so.6
#3  0x083e79c7 in wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:88
#4  QWaitCondition::wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:160
#5  0x007ac030 in ThreadWeaver::WeaverImpl::blockThreadUntilJobsAreBeingAssigned (this=0xa690808, th=0xab3ac58) at ../../../threadweaver/Weaver/WeaverImpl.cpp:365
#6  0x007af7dc in ThreadWeaver::WorkingHardState::waitForAvailableJob (this=0xa6909d0, th=0xab3ac58) at ../../../threadweaver/Weaver/WorkingHardState.cpp:80
#7  0x007ab55b in ThreadWeaver::WeaverImpl::waitForAvailableJob (this=0xa690808, th=0xab3ac58) at ../../../threadweaver/Weaver/WeaverImpl.cpp:356
#8  0x007af8d2 in ThreadWeaver::WorkingHardState::applyForWork (this=0xa6909d0, th=0xab3ac58) at ../../../threadweaver/Weaver/WorkingHardState.cpp:71
#9  0x007ac533 in ThreadWeaver::WeaverImpl::applyForWork (this=0xa690808, th=0xab3ac58, previous=0xa8b3d68) at ../../../threadweaver/Weaver/WeaverImpl.cpp:351
#10 0x007ad95e in ThreadWeaver::ThreadRunHelper::run (this=0xace912e4, parent=0xa690808, th=0xab3ac58) at ../../../threadweaver/Weaver/Thread.cpp:87
#11 0x007ae07b in ThreadWeaver::Thread::run (this=0xab3ac58) at ../../../threadweaver/Weaver/Thread.cpp:142
#12 0x083e6df9 in QThreadPrivate::start (arg=0xab3ac58) at thread/qthread_unix.cpp:266
#13 0x0076acc9 in start_thread () from /lib/libpthread.so.0
#14 0x001e069e in clone () from /lib/libc.so.6

Thread 2 (Thread 0xac690b70 (LWP 3425)):
#0  0x007b9416 in __kernel_vsyscall ()
#1  0x0076f4dc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0x001edd9d in pthread_cond_wait () from /lib/libc.so.6
#3  0x083e79c7 in wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:88
#4  QWaitCondition::wait (this=0xa690820, mutex=0xa6903b8, time=4294967295) at thread/qwaitcondition_unix.cpp:160
#5  0x007ac030 in ThreadWeaver::WeaverImpl::blockThreadUntilJobsAreBeingAssigned (this=0xa690808, th=0x9d240c8) at ../../../threadweaver/Weaver/WeaverImpl.cpp:365
#6  0x007af7dc in ThreadWeaver::WorkingHardState::waitForAvailableJob (this=0xa6909d0, th=0x9d240c8) at ../../../threadweaver/Weaver/WorkingHardState.cpp:80
#7  0x007ab55b in ThreadWeaver::WeaverImpl::waitForAvailableJob (this=0xa690808, th=0x9d240c8) at ../../../threadweaver/Weaver/WeaverImpl.cpp:356
#8  0x007af8d2 in ThreadWeaver::WorkingHardState::applyForWork (this=0xa6909d0, th=0x9d240c8) at ../../../threadweaver/Weaver/WorkingHardState.cpp:71
#9  0x007ac533 in ThreadWeaver::WeaverImpl::applyForWork (this=0xa690808, th=0x9d240c8, previous=0xa8a78b8) at ../../../threadweaver/Weaver/WeaverImpl.cpp:351
#10 0x007ad95e in ThreadWeaver::ThreadRunHelper::run (this=0xac6902e4, parent=0xa690808, th=0x9d240c8) at ../../../threadweaver/Weaver/Thread.cpp:87
#11 0x007ae07b in ThreadWeaver::Thread::run (this=0x9d240c8) at ../../../threadweaver/Weaver/Thread.cpp:142
#12 0x083e6df9 in QThreadPrivate::start (arg=0x9d240c8) at thread/qthread_unix.cpp:266
#13 0x0076acc9 in start_thread () from /lib/libpthread.so.0
#14 0x001e069e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb782b720 (LWP 2948)):
[KCrash Handler]
#7  0x02fc19a2 in findActionItemForAction (this=0xa8ae298, event=0xbf8890b8) at /build/buildd/plasma-widget-message-indicator-0.5.6/src/listenermodel.cpp:189
#8  removeAction (this=0xa8ae298, event=0xbf8890b8) at /build/buildd/plasma-widget-message-indicator-0.5.6/src/listenermodel.cpp:177
#9  ServerItem::eventFilter (this=0xa8ae298, event=0xbf8890b8) at /build/buildd/plasma-widget-message-indicator-0.5.6/src/listenermodel.cpp:150
#10 0x084e829a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x9c5f848, receiver=0xa8a9ca0, event=0xbf8890b8) at kernel/qcoreapplication.cpp:847
#11 0x056d5fb9 in QApplicationPrivate::notify_helper (this=0x9c5f848, receiver=0xa8a9ca0, e=0xbf8890b8) at kernel/qapplication.cpp:4392
#12 0x056dc0e9 in QApplication::notify (this=0x9c546a0, receiver=0xa8a9ca0, e=0xbf8890b8) at kernel/qapplication.cpp:4361
#13 0x0105968a in KApplication::notify (this=0x9c546a0, receiver=0xa8a9ca0, event=0xbf8890b8) at ../../kdeui/kernel/kapplication.cpp:310
#14 0x084e8b3b in QCoreApplication::notifyInternal (this=0x9c546a0, receiver=0xa8a9ca0, event=0xbf8890b8) at kernel/qcoreapplication.cpp:732
#15 0x0572958a in sendEvent (this=0xa8a9ca0, action=0xa5e40c8) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#16 QWidget::removeAction (this=0xa8a9ca0, action=0xa5e40c8) at kernel/qwidget.cpp:3169
#17 0x05b9ace8 in QMenu::clear (this=0xa8a9ca0) at widgets/qmenu.cpp:1714
#18 0x0294149b in DBusMenuImporter::GetChildrenCallback(int, QDBusPendingCallWatcher*) () from /usr/lib/libdbusmenu-qt.so.2
#19 0x0294047e in DBusMenuImporter::dispatch(QDBusPendingCallWatcher*) () from /usr/lib/libdbusmenu-qt.so.2
#20 0x02944eaf in DBusMenuImporter::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libdbusmenu-qt.so.2
#21 0x084ee8ca in QMetaObject::metacall (object=0xa921e88, cl=QMetaObject::InvokeMetaMethod, idx=8, argv=0xbf889418) at kernel/qmetaobject.cpp:237
#22 0x085016ad in QMetaObject::activate (sender=0xac27028, m=0xddfb68, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3280
#23 0x00dc39c3 in QDBusPendingCallWatcher::finished (this=0xac27028, _t1=0xac27028) at .moc/release-shared/moc_qdbuspendingcall.cpp:92
#24 0x00dc3a5a in _q_finished (this=0xac27028, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0xaa34248) at qdbuspendingcall.cpp:482
#25 QDBusPendingCallWatcher::qt_metacall (this=0xac27028, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0xaa34248) at .moc/release-shared/moc_qdbuspendingcall.cpp:80
#26 0x084ee8ca in QMetaObject::metacall (object=0xac27028, cl=QMetaObject::InvokeMetaMethod, idx=5, argv=0xaa34248) at kernel/qmetaobject.cpp:237
#27 0x084f9df6 in QMetaCallEvent::placeMetaCall (this=0xa720098, object=0xac27028) at kernel/qobject.cpp:534
#28 0x084fb6a2 in QObject::event (this=0xac27028, e=0xa5e40c8) at kernel/qobject.cpp:1219
#29 0x056d5fdc in QApplicationPrivate::notify_helper (this=0x9c5f848, receiver=0xac27028, e=0xa720098) at kernel/qapplication.cpp:4396
#30 0x056dc04e in QApplication::notify (this=0x9c546a0, receiver=0xac27028, e=0xa720098) at kernel/qapplication.cpp:3798
#31 0x0105968a in KApplication::notify (this=0x9c546a0, receiver=0xac27028, event=0xa720098) at ../../kdeui/kernel/kapplication.cpp:310
#32 0x084e8b3b in QCoreApplication::notifyInternal (this=0x9c546a0, receiver=0xac27028, event=0xa720098) at kernel/qcoreapplication.cpp:732
#33 0x084ebd8b in sendEvent (receiver=0x0, event_type=0, data=0x9c3e040) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#34 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x9c3e040) at kernel/qcoreapplication.cpp:1373
#35 0x084ebf4d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1266
#36 0x08517a74 in sendPostedEvents (s=0x9c61b78) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#37 postEventSourceDispatch (s=0x9c61b78) at kernel/qeventdispatcher_glib.cpp:277
#38 0x046c5855 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#39 0x046c9668 in ?? () from /lib/libglib-2.0.so.0
#40 0x046c9848 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#41 0x08517565 in QEventDispatcherGlib::processEvents (this=0x9c3dd00, flags=...) at kernel/qeventdispatcher_glib.cpp:415
#42 0x05797be5 in QGuiEventDispatcherGlib::processEvents (this=0x9c3dd00, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#43 0x084e7609 in QEventLoop::processEvents (this=0xbf889c54, flags=) at kernel/qeventloop.cpp:149
#44 0x084e7a8a in QEventLoop::exec (this=0xbf889c54, flags=...) at kernel/qeventloop.cpp:201
#45 0x084ec00f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1009
#46 0x056d4e07 in QApplication::exec () at kernel/qapplication.cpp:3672
#47 0x0053c86e in kdemain (argc=1, argv=0xbf889e64) at ../../../../plasma/desktop/shell/main.cpp:118
#48 0x080485bb in main (argc=1, argv=0xbf889e64) at plasma-desktop_dummy.cpp:3