Version:            (using KDE 4.2.0)
OS:                Linux
Installed from:    SuSE RPMs

Plasma crashes randomly with signal sigsev. 
I have installed the debug-sources and hope that this will help you out:

Anwendung: Plasma-Desktop (plasma), Signal SIGSEGV
[?1034h[Thread debugging using libthread_db enabled]
[Current thread is 1 (Thread 0xb5286700 (LWP 11894))]

Thread 3 (Thread 0xa9ad0b90 (LWP 11901)):
#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb6567c35 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb65c7872 in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQtCore.so.4
#3  0xb79c40d2 in ?? () from /usr/lib/libQtNetwork.so.4
#4  0xb65c685e in ?? () from /usr/lib/libQtCore.so.4
#5  0xb65641b5 in start_thread () from /lib/libpthread.so.0
#6  0xb63a63be in clone () from /lib/libc.so.6

Thread 2 (Thread 0xa926fb90 (LWP 11902)):
#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb6567c35 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb65c7872 in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQtCore.so.4
#3  0xa9c1280a in RenderThread::run (this=0x82256fc) at /usr/src/debug/kdebase-workspace-4.2.0/plasma/wallpapers/image/renderthread.cpp:91
#4  0xb65c685e in ?? () from /usr/lib/libQtCore.so.4
#5  0xb65641b5 in start_thread () from /lib/libpthread.so.0
#6  0xb63a63be in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb5286700 (LWP 11894)):
[KCrash Handler]
#6  0xa9cf8f22 in WindowTaskItem::setAdditionalMimeData (this=0x86ce660, mimeData=0x83abf68) at /usr/src/debug/kdebase-workspace-4.2.0/plasma/applets/tasks/windowtaskitem.cpp:298
#7  0xa9d01678 in AbstractTaskItem::mouseMoveEvent (this=0x86ce660, event=0xbfc3aca0) at /usr/src/debug/kdebase-workspace-4.2.0/plasma/applets/tasks/abstracttaskitem.cpp:287
#8  0xb6ea1a02 in QGraphicsItem::sceneEvent(QEvent*) () from /usr/lib/libQtGui.so.4
#9  0xb6ee4f0f in QGraphicsWidget::sceneEvent(QEvent*) () from /usr/lib/libQtGui.so.4
#10 0xb6ebfd2c in ?? () from /usr/lib/libQtGui.so.4
#11 0xb6ec0f1a in ?? () from /usr/lib/libQtGui.so.4
#12 0xb6ec8d4d in QGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent*) () from /usr/lib/libQtGui.so.4
#13 0xb6ec8fa7 in QGraphicsScene::event(QEvent*) () from /usr/lib/libQtGui.so.4
#14 0xb69268fc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#15 0xb692e75e in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#16 0xb771293d in KApplication::notify (this=0x805e920, receiver=0x80622f0, event=0xbfc3aca0) at /usr/src/debug/kdelibs-4.2.0/kdeui/kernel/kapplication.cpp:307
#17 0xb66b6961 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#18 0xb6ed6578 in ?? () from /usr/lib/libQtGui.so.4
#19 0xb6edea76 in QGraphicsView::mouseMoveEvent(QMouseEvent*) () from /usr/lib/libQtGui.so.4
#20 0xb697e8cb in QWidget::event(QEvent*) () from /usr/lib/libQtGui.so.4
#21 0xb6cb4a83 in QFrame::event(QEvent*) () from /usr/lib/libQtGui.so.4
#22 0xb6d4b1bf in QAbstractScrollArea::viewportEvent(QEvent*) () from /usr/lib/libQtGui.so.4
#23 0xb6ed84df in QGraphicsView::viewportEvent(QEvent*) () from /usr/lib/libQtGui.so.4
#24 0xb6d4d765 in ?? () from /usr/lib/libQtGui.so.4
#25 0xb66b5b3a in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#26 0xb69268da in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#27 0xb692f111 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#28 0xb771293d in KApplication::notify (this=0x805e920, receiver=0x838d920, event=0xbfc3b358) at /usr/src/debug/kdelibs-4.2.0/kdeui/kernel/kapplication.cpp:307
#29 0xb66b6961 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#30 0xb692e39e in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&) () from /usr/lib/libQtGui.so.4
#31 0xb6998716 in ?? () from /usr/lib/libQtGui.so.4
#32 0xb6997ac5 in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/libQtGui.so.4
#33 0xb69c008a in ?? () from /usr/lib/libQtGui.so.4
#34 0xb56969a8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#35 0xb569a063 in ?? () from /usr/lib/libglib-2.0.so.0
#36 0xb569a221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#37 0xb66e0fb8 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#38 0xb69bf785 in ?? () from /usr/lib/libQtGui.so.4
#39 0xb66b501a in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#40 0xb66b51da in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#41 0xb66b7895 in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#42 0xb6926777 in QApplication::exec() () from /usr/lib/libQtGui.so.4
#43 0xb7fb2336 in kdemain (argc=1, argv=0xbfc3bd54) at /usr/src/debug/kdebase-workspace-4.2.0/plasma/shells/desktop/main.cpp:54
#44 0x08048782 in main (argc=1371, argv=0x804c5f8) at /usr/src/debug/kdebase-workspace-4.2.0/build/plasma/shells/desktop/plasma_qgv_dummy.cpp:3