Version:            (using KDE 4.2.98)
OS:                Linux
Installed from:    SuSE RPMs

when i start two or more applications FAST one after another, there are five possibilities of what happens to plasma (or some part of plasma), see below. 

what did i do: i started the applications (i tried okular, gwenview and konsole) by klicking on files in the file-manager (dolphin). i think this is the fastest way to start apllications, and the only way i could reproduce the issue. 

1.) everything works as expected and all windows appear in the taskbar (this is what happens around 18 times out of every 20 times i tried.

2.) for some time, the taskbar has a strange appearance (see taskbar1.png). when i recall it correctly, after around 30 seconds the appearance bacame normal again. 

3.) the taskbar shows some kind of "dead window", see the empty okular window in taskbar2.png. this does not disappear, plasma has to be restarted to get it away. (when i created the screenshot, the okular tast was definitely not running anymore) another example is taskbar3.png, see the gwenview task there. 

4.) the whole plasma panel disappears and then restarts, without a crash

5.) plasma crashes (see backtrace) and then restarts by itself.

backtrace:

Application: Plasma-Arbeitsfläche (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0x7f8212f5b750 (LWP 25425))]

Thread 2 (Thread 0x7f81f1ab6950 (LWP 25427)):
#0  0x00007f821272dd59 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f821299ee19 in QWaitCondition::wait (this=0x1b23e30, mutex=0x1b23e28, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f82115d287c in QHostInfoAgent::run (this=0x1b23e10) at kernel/qhostinfo.cpp:260
#3  0x00007f821299de65 in QThreadPrivate::start (arg=0x1b23e10) at thread/qthread_unix.cpp:188
#4  0x00007f821272a070 in start_thread () from /lib64/libpthread.so.0
#5  0x00007f820f28810d in clone () from /lib64/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f8212f5b750 (LWP 25425)):
[KCrash Handler]
#5  0x00007f82103f6794 in QGraphicsLayoutItem::geometry (this=0x740086) at graphicsview/qgraphicslayoutitem.cpp:664
#6  0x00007f82103fa1a5 in QGraphicsWidget::size (this=<value optimized out>) at graphicsview/qgraphicswidget.cpp:336
#7  0x00007f81f4a4fdbf in AbstractTaskItem::basicPreferredSize (this=0x20e4c50) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/applets/tasks/abstracttaskitem.cpp:105
#8  0x00007f81f4a4c3e2 in TaskItemLayout::maximumRows (this=0x1b23340) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/applets/tasks/taskitemlayout.cpp:185
#9  0x00007f81f4a54a77 in TaskGroupItem::optimumCapacity (this=0x1b80350) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/applets/tasks/taskgroupitem.cpp:1224
#10 0x00007f81f4a47d40 in Tasks::adjustGroupingStrategy (this=0xbe94e0) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/applets/tasks/tasks.cpp:241
#11 0x00007f81f4a47f58 in Tasks::constraintsEvent (this=0xbe94e0, constraints={i = 7602310}) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/applets/tasks/tasks.cpp:165
#12 0x00007f8209e3fc59 in Plasma::Applet::flushPendingConstraintsEvents() () from /usr/lib64/libplasma.so.3
#13 0x00007f8209e40325 in Plasma::Applet::timerEvent(QTimerEvent*) () from /usr/lib64/libplasma.so.3
#14 0x00007f8212a97533 in QObject::event (this=0xbe94e0, e=0x740086) at kernel/qobject.cpp:1075
#15 0x00007f82103fb26b in QGraphicsWidget::event (this=0xbe94e0, event=0x7fff09b2f030) at graphicsview/qgraphicswidget.cpp:1340
#16 0x00007f820fe26b0d in QApplicationPrivate::notify_helper (this=0x672ef0, receiver=0xbe94e0, e=0x7fff09b2f030) at kernel/qapplication.cpp:4056
#17 0x00007f820fe2ed9a in QApplication::notify (this=0x66a140, receiver=0xbe94e0, e=0x7fff09b2f030) at kernel/qapplication.cpp:4021
#18 0x00007f8210f1071b in KApplication::notify(QObject*, QEvent*) () from /usr/lib64/libkdeui.so.5
#19 0x00007f8212a8794c in QCoreApplication::notifyInternal (this=0x66a140, receiver=0xbe94e0, event=0x7fff09b2f030) at kernel/qcoreapplication.cpp:610
#20 0x00007f8212ab4b60 in QTimerInfoList::activateTimers (this=0x6766b0) at kernel/qcoreapplication.h:213
#21 0x00007f8212ab0ddd in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:165
#22 0x00007f820e9060fb in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#23 0x00007f820e9098cd in ?? () from /usr/lib64/libglib-2.0.so.0
#24 0x00007f820e909a8b in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#25 0x00007f8212ab0d3f in QEventDispatcherGlib::processEvents (this=0x618640, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#26 0x00007f820febdfff in QGuiEventDispatcherGlib::processEvents (this=0x7fff09b2e5a0, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#27 0x00007f8212a861d2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 162722640}) at kernel/qeventloop.cpp:149
#28 0x00007f8212a865a4 in QEventLoop::exec (this=0x7fff09b2f390, flags={i = 162722720}) at kernel/qeventloop.cpp:201
#29 0x00007f8212a88894 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#30 0x00007f8207188aeb in kdemain (argc=1, argv=0x614e00) at /usr/src/debug/kdebase-workspace-4.2.98/plasma/shells/desktop/main.cpp:50
#31 0x0000000000407495 in _start ()