This seems to be a Qt4.4.x bug, already fixed for 4.4.4 and 4.5 (+ qt-copy).
Like bug 185647, bug 183055, bug 182351, and bug 182125
Please, update your Qt4 package. Thanks

Sorry forgot to mention that this was on QT-4.5 (on Fedora 11 rawhide).
Please re-open.

Strange. Do you know if the KDE packages are properly compiled against Qt4.5 ? (It shouldn't affect, but I'm trying to get some info).
Also, please install "kdelibs5-debuginfo" and "libqt4-debuginfo" and post a new backtrace (hopefully more complete) here.
Thanks

Yes, those are the packages shipped by fedora rawhide - and they were compiled against QT-4.5. However shouldn't make any difference.

I already have the debug packages installed, unfourtunatly the crash happend before. I'll see what I can do to krash plasma again...

Created attachment 32155 [details]
Full backtrace with debugging symbols installed

finally managed to get the crash again

Thanks.
Pasted backtrace from comment 5:
------

Application: Plasma Workspace (plasma), signal SIGSEGV
0x009f9c4c in nanosleep () from /lib/libc.so.6
[Current thread is 1 (Thread 0xb7f16780 (LWP 2781))]

Thread 4 (Thread 0xace55b70 (LWP 2782)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S:123
#1  0x05213557 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:87
#2  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#3  0x05477eda in QHostInfoAgent::run (this=0x93e6d40) at kernel/qhostinfo.cpp:260
#4  0x052124ee in QThreadPrivate::start (arg=0x93e6d40) at thread/qthread_unix.cpp:189
#5  0x00b067d7 in start_thread (arg=0xace55b70) at pthread_create.c:297
#6  0x00a3ba0e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 3 (Thread 0xac2ffb70 (LWP 2783)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S:123
#1  0x05213557 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:87
#2  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#3  0x044fa1ea in ?? () from /usr/lib/kde4/plasma_wallpaper_image.so
#4  0x052124ee in QThreadPrivate::start (arg=0x92bca94) at thread/qthread_unix.cpp:189
#5  0x00b067d7 in start_thread (arg=0xac2ffb70) at pthread_create.c:297
#6  0x00a3ba0e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130
Current language:  auto; currently asm

Thread 2 (Thread 0xa5e7fb70 (LWP 3273)):
#0  0x00a33ff7 in select () from /lib/libc.so.6
#1  0x052e29f5 in QProcessManager::run (this=0x9035368) at io/qprocess_unix.cpp:305
#2  0x052124ee in QThreadPrivate::start (arg=0x9035368) at thread/qthread_unix.cpp:189
#3  0x00b067d7 in start_thread (arg=0xa5e7fb70) at pthread_create.c:297
#4  0x00a3ba0e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 1 (Thread 0xb7f16780 (LWP 2781)):
[KCrash Handler]
#5  0x00c4ad6a in ?? () from /usr/lib/libX11.so.6
#6  0x07378675 in Plasma::ContainmentPrivate::focusApplet (this=0x9122078, applet=0x91a9148) at /usr/src/debug/kdelibs-4.2.1/plasma/containment.cpp:1402
#7  0x073647f3 in Plasma::Applet::focusInEvent (this=0x91a9148, event=0xbfa3cd3c) at /usr/src/debug/kdelibs-4.2.1/plasma/applet.cpp:1344
#8  0x05ec93d2 in QGraphicsItem::sceneEvent (this=0x91a9150, event=0xbfa3cd3c) at graphicsview/qgraphicsitem.cpp:4756
#9  0x05f15b2f in QGraphicsWidget::sceneEvent (this=0x91a9148, event=0xbfa3cd3c) at graphicsview/qgraphicswidget.cpp:1089
#10 0x05eee8fc in QGraphicsScenePrivate::sendEvent (this=0x90c5468, item=0x91a9150, event=0xbfa3cd3c) at graphicsview/qgraphicsscene.cpp:1150
#11 0x05eef353 in QGraphicsScene::setFocusItem (this=0x90be5e8, item=0x91a9150, focusReason=Qt::MouseFocusReason) at graphicsview/qgraphicsscene.cpp:3249
#12 0x05ef3d4b in QGraphicsScenePrivate::mousePressEventHandler (this=0x90c5468, mouseEvent=0xbfa3d284) at graphicsview/qgraphicsscene.cpp:1262
#13 0x05ef56f7 in QGraphicsScene::event (this=0x90be5e8, event=0xbfa3d284) at graphicsview/qgraphicsscene.cpp:3658
#14 0x0588ca3c in QApplicationPrivate::notify_helper (this=0x9036028, receiver=0x90be5e8, e=0xbfa3d284) at kernel/qapplication.cpp:4084
#15 0x05893e84 in QApplication::notify (this=0x902d990, receiver=0x90be5e8, e=0xbfa3d284) at kernel/qapplication.cpp:4049
#16 0x062ffd0a in KApplication::notify (this=0x902d990, receiver=0x90be5e8, event=0xbfa3d284) at /usr/src/debug/kdelibs-4.2.1/kdeui/kernel/kapplication.cpp:307
#17 0x05304deb in QCoreApplication::notifyInternal (this=0x902d990, receiver=0x90be5e8, event=0xbfa3d284) at kernel/qcoreapplication.cpp:602
#18 0x05f05c21 in QCoreApplication::sendEvent (event=<value optimized out>, receiver=<value optimized out>) at ../../src/corelib/kernel/qcoreapplication.h:213
#19 QGraphicsView::mousePressEvent (event=<value optimized out>, receiver=<value optimized out>) at graphicsview/qgraphicsview.cpp:3226
#20 0x058e227b in QWidget::event (this=0x9569850, event=0xbfa3d8a0) at kernel/qwidget.cpp:7512
#21 0x05cc1f73 in QFrame::event (this=0x9569850, e=0xbfa3d8a0) at widgets/qframe.cpp:559
#22 0x05d61ff4 in QAbstractScrollArea::viewportEvent (this=0x1020201, e=0x10a25562) at widgets/qabstractscrollarea.cpp:962
#23 0x05f06a0f in QGraphicsView::viewportEvent (this=0x9569850, event=0xbfa3d8a0) at graphicsview/qgraphicsview.cpp:2933
#24 0x05d64635 in QAbstractScrollAreaPrivate::viewportEvent (this=<value optimized out>, event=<value optimized out>, this=<value optimized out>, event=<value optimized out>)
    at widgets/qabstractscrollarea_p.h:100
#25 QAbstractScrollAreaFilter::eventFilter (this=<value optimized out>, event=<value optimized out>, this=<value optimized out>, event=<value optimized out>) at widgets/qabstractscrollarea_p.h:111
#26 0x05303f3a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x9036028, receiver=0x956ae78, event=0xbfa3d8a0) at kernel/qcoreapplication.cpp:718
#27 0x0588ca1a in QApplicationPrivate::notify_helper (this=0x9036028, receiver=0x956ae78, e=0xbfa3d8a0) at kernel/qapplication.cpp:4080
#28 0x0589475b in QApplication::notify (this=0x902d990, receiver=0x956ae78, e=0xbfa3d8a0) at kernel/qapplication.cpp:3786
#29 0x062ffd0a in KApplication::notify (this=0x902d990, receiver=0x956ae78, event=0xbfa3d8a0) at /usr/src/debug/kdelibs-4.2.1/kdeui/kernel/kapplication.cpp:307
#30 0x05304deb in QCoreApplication::notifyInternal (this=0x902d990, receiver=0x956ae78, event=0xbfa3d8a0) at kernel/qcoreapplication.cpp:602
#31 0x058937de in QCoreApplication::sendSpontaneousEvent (event=<value optimized out>, receiver=<value optimized out>) at ../../src/corelib/kernel/qcoreapplication.h:216
#32 QApplicationPrivate::sendMouseEvent (event=<value optimized out>, receiver=<value optimized out>) at kernel/qapplication.cpp:2940
#33 0x05902aa0 in QETWidget::translateMouseEvent (this=0x9569850, event=0xbfa3de9c) at kernel/qapplication_x11.cpp:4425
#34 0x05901f52 in QApplication::x11ProcessEvent (this=0x902d990, event=0xbfa3de9c) at kernel/qapplication_x11.cpp:3421
#35 0x0592cf42 in x11EventSourceDispatch (s=0x903cf68, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#36 0x05119188 in g_main_dispatch (context=<value optimized out>) at gmain.c:1814
#37 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2367
#38 0x0511c798 in g_main_context_iterate (context=0x903c490, block=<value optimized out>, dispatch=1, self=0x9035b58) at gmain.c:2448
#39 0x0511c90a in IA__g_main_context_iteration (context=0x903c490, may_block=1) at gmain.c:2511
#40 0x0533036c in QEventDispatcherGlib::processEvents (this=0x9020d88, flags={i = 36}) at kernel/qeventdispatcher_glib.cpp:323
#41 0x0592c625 in QGuiEventDispatcherGlib::processEvents (this=0x9020d88, flags={i = 36}) at kernel/qguieventdispatcher_glib.cpp:202
#42 0x05303379 in QEventLoop::processEvents (this=0xbfa3e194, flags=) at kernel/qeventloop.cpp:149
#43 0x053037c2 in QEventLoop::exec (this=0xbfa3e194, flags={i = 0}) at kernel/qeventloop.cpp:200
#44 0x05305b4f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#45 0x0588c8b7 in QApplication::exec () at kernel/qapplication.cpp:3553
#46 0x06838686 in kdemain () from /usr/lib/libkdeinit4_plasma.so
#47 0x080486eb in _start ()
Current language:  auto; currently c

I wonder about the first line: #5  0x00c4ad6a in ?? () from /usr/lib/libX11.so.6
The rest of the backtrace looks mostly the same as bug 176510 (upstream, fixed in Qt4.5). So I don't know if the issue wasn't properly fixed or this is a new and different case.

This could be bug 192589. Perhaps the mouse slipped and an applet moved to the desktop, triggering that crash?

I tried it today with KDE-4.2.3 and it happend again.
This time I made absolutly sure the mouse didn't slip - plasma crashed by simple resizing the panel at a very fast rate (the crash happend when the panel was resized to very small):

Application: Plasma Workspace (plasma), signal SIGSEGV
__kernel_vsyscall () at arch/x86/vdso/vdso32/int80.S:16
16		ret
Current language:  auto; currently asm
[Current thread is 1 (Thread 0xb7f3d780 (LWP 2170))]

Thread 3 (Thread 0xace70b70 (LWP 2172)):
#0  __kernel_vsyscall () at arch/x86/vdso/vdso32/int80.S:16
#1  0x008a3fa5 in pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S:122
#2  0x061b1ef7 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:87
#3  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#4  0x079ced8a in QHostInfoAgent::run (this=0x8a23d38) at kernel/qhostinfo.cpp:260
#5  0x061b0e8e in QThreadPrivate::start (arg=0x8a23d38) at thread/qthread_unix.cpp:189
#6  0x0089f935 in start_thread (arg=0xace70b70) at pthread_create.c:297
#7  0x00edc82e in clone () from /lib/libc.so.6

Thread 2 (Thread 0xac2ffb70 (LWP 2173)):
#0  __kernel_vsyscall () at arch/x86/vdso/vdso32/int80.S:16
#1  0x008a3fa5 in pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S:122
#2  0x061b1ef7 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:87
#3  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#4  0x014d60ca in RenderThread::run (this=0x886f3fc) at /usr/src/debug/kdebase-workspace-4.2.3/plasma/wallpapers/image/renderthread.cpp:91
#5  0x061b0e8e in QThreadPrivate::start (arg=0x886f3fc) at thread/qthread_unix.cpp:189
#6  0x0089f935 in start_thread (arg=0xac2ffb70) at pthread_create.c:297
#7  0x00edc82e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb7f3d780 (LWP 2170)):
[KCrash Handler]
#6  QWidget::mapToParent (this=0x0, pos=@0xbfd689a8) at kernel/qwidget.cpp:3830
#7  0x0703e3cb in QWidget::mapTo (this=0x0, parent=0x8b16ce0, pos=@0xbfd689bc) at kernel/qwidget.cpp:3786
#8  0x0720f643 in qt_flush (tlwOffset=<value optimized out>, tlw=<value optimized out>, windowSurface=<value optimized out>, region=<value optimized out>, widget=<value optimized out>)
    at painting/qbackingstore.cpp:98
#9  QWidgetBackingStore::flush (tlwOffset=<value optimized out>, tlw=<value optimized out>, windowSurface=<value optimized out>, region=<value optimized out>, widget=<value optimized out>)
    at painting/qbackingstore.cpp:1338
#10 0x07210cd1 in QWidgetBackingStore::sync (this=0x8adb268) at painting/qbackingstore.cpp:1269
#11 0x07045746 in QWidgetPrivate::syncBackingStore (this=0x8b16f90) at kernel/qwidget.cpp:1603
#12 0x0704ca33 in QWidget::event (this=0x8b16ce0, event=0x9434d78) at kernel/qwidget.cpp:7794
#13 0x0742bc93 in QFrame::event (this=0x8b16ce0, e=0x9434d78) at widgets/qframe.cpp:559
#14 0x074cc7ca in QAbstractScrollArea::event (this=0x8b16ce0, e=0x9434d78) at widgets/qabstractscrollarea.cpp:918
#15 0x076703e6 in QGraphicsView::event (this=0x8b16ce0, event=0x9434d78) at graphicsview/qgraphicsview.cpp:2854
#16 0x00498fd3 in PanelView::event (this=0x8b16ce0, event=0x9434d78) at /usr/src/debug/kdebase-workspace-4.2.3/plasma/shells/desktop/panelview.cpp:1191
#17 0x06ff6cfc in QApplicationPrivate::notify_helper (this=0x85c7338, receiver=0x8b16ce0, e=0x9434d78) at kernel/qapplication.cpp:4084
#18 0x06ffe124 in QApplication::notify (this=0x85b9858, receiver=0x8b16ce0, e=0x9434d78) at kernel/qapplication.cpp:4049
#19 0x0116605a in KApplication::notify (this=0x85b9858, receiver=0x8b16ce0, event=0x9434d78) at /usr/src/debug/kdelibs-4.2.3/kdeui/kernel/kapplication.cpp:307
#20 0x062a36db in QCoreApplication::notifyInternal (this=0x85b9858, receiver=0x8b16ce0, event=0x9434d78) at kernel/qcoreapplication.cpp:602
#21 0x062a41a8 in QCoreApplication::sendEvent (event=<value optimized out>, receiver=<value optimized out>) at kernel/qcoreapplication.h:213
#22 QCoreApplicationPrivate::sendPostedEvents (event=<value optimized out>, receiver=<value optimized out>) at kernel/qcoreapplication.cpp:1239
#23 0x062a437d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1132
#24 0x062cef9f in QCoreApplication::sendPostedEvents () at kernel/qcoreapplication.h:218
#25 postEventSourceDispatch () at kernel/qeventdispatcher_glib.cpp:209
#26 0x083941e8 in g_main_dispatch (context=<value optimized out>) at gmain.c:1814
#27 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2367
#28 0x083977f8 in g_main_context_iterate (context=0x85c9490, block=<value optimized out>, dispatch=1, self=0x85c6b40) at gmain.c:2448
#29 0x0839796a in IA__g_main_context_iteration (context=0x85c9490, may_block=1) at gmain.c:2511
#30 0x062cebcc in QEventDispatcherGlib::processEvents (this=0x859d000, flags={i = 36}) at kernel/qeventdispatcher_glib.cpp:323
#31 0x07096825 in QGuiEventDispatcherGlib::processEvents (this=0x859d000, flags={i = 36}) at kernel/qguieventdispatcher_glib.cpp:202
#32 0x062a1c69 in QEventLoop::processEvents (this=0xbfd694b4, flags=) at kernel/qeventloop.cpp:149
#33 0x062a20b2 in QEventLoop::exec (this=0xbfd694b4, flags={i = 0}) at kernel/qeventloop.cpp:200
#34 0x062a443f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#35 0x06ff6b77 in QApplication::exec () at kernel/qapplication.cpp:3553
#36 0x0048f786 in kdemain (argc=1, argv=0xbfd69694) at /usr/src/debug/kdebase-workspace-4.2.3/plasma/shells/desktop/main.cpp:54
#37 0x080486eb in main (argc=1, argv=0xbfd69694) at /usr/src/debug/kdebase-workspace-4.2.3/i586-redhat-linux-gnu/plasma/shells/desktop/plasma_qgv_dummy.cpp:3

This is probably a dupe of bug 192589.

@Clemens Eisserer: your last backtrace is different, please file a new bug report. 
Marking as dupe of bug 192589. Thanks

*** This bug has been marked as a duplicate of bug 192589 ***