Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.3.2 (KDE 4.3.2)
Qt Version: 4.5.3
Operating System: Linux 2.6.30-2-amd64 x86_64
Distribution: Debian GNU/Linux unstable (sid)

What I was doing when the application crashed:
Mi setup is that I use 4 desktops and have multiple applications instances  "collapsed" in the taskbar, and each desktop has it's own programs. I've  noticed that sometime I have the leftmost position of taskbar empty instead of showing the first item for the programs open for that desktop. If then I switch to another desktop, I have this crash.

 -- Backtrace:
Application: Spazio di lavoro di Plasma (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0x7f9c72c2e750 (LWP 3452))]

Thread 2 (Thread 0x7f9c5462a950 (LWP 3453)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f9c72775499 in QWaitConditionPrivate::wait (this=0x102c970, mutex=0x102c968, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  QWaitCondition::wait (this=0x102c970, mutex=0x102c968, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:159
#3  0x00007f9c6eb713b4 in QHostInfoAgent::run (this=0x102c950) at kernel/qhostinfo.cpp:260
#4  0x00007f9c727744a5 in QThreadPrivate::start (arg=0x102c950) at thread/qthread_unix.cpp:188
#5  0x00007f9c6f4aef9a in start_thread (arg=<value optimized out>) at pthread_create.c:300
#6  0x00007f9c7007756d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#7  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f9c72c2e750 (LWP 3452)):
[KCrash Handler]
#5  QGraphicsItem::parentItem (this=0x2b) at graphicsview/qgraphicsitem.cpp:939
#6  0x00007f9c70dc1543 in QGraphicsLayoutPrivate::addChildLayoutItem (this=0x111ef80, layoutItem=<value optimized out>) at graphicsview/qgraphicslayout_p.cpp:162
#7  0x00007f9c70ddb7db in QGraphicsGridLayout::addItem (this=0x111b080, item=0x111b080, row=0, column=0, rowSpan=1, columnSpan=1, alignment=...) at graphicsview/qgraphicsgridlayout.cpp:158
#8  0x00007f9c55fe91b6 in TaskItemLayout::layoutItems (this=0x111b080) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:370
#9  0x00007f9c55fe97b9 in TaskItemLayout::remove (this=0x111b080, item=0x1fca180) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:136
#10 0x00007f9c55fe985e in TaskItemLayout::removeTaskItem (this=0x2b, item=0x111b080) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:93
#11 0x00007f9c55ff47f9 in TaskGroupItem::itemRemoved (this=0x111ed90, groupableItem=0x1c69590) at ../../../../plasma/applets/tasks/taskgroupitem.cpp:521
#12 0x00007f9c55ff5c11 in TaskGroupItem::qt_metacall (this=0x111ed90, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffbbf5baf0) at ./taskgroupitem.moc:114
#13 0x00007f9c7286edf2 in QMetaObject::activate (sender=0x111b620, from_signal_index=<value optimized out>, to_signal_index=22, argv=0x0) at kernel/qobject.cpp:3112
#14 0x00007f9c5622f072 in TaskManager::TaskGroup::itemRemoved (this=0x2b, _t1=0x1c69590) at ./taskgroup.moc:152
#15 0x00007f9c5622f981 in TaskManager::TaskGroup::remove (this=0x111b620, item=0x1c69590) at ../../../libs/taskmanager/taskgroup.cpp:189
#16 0x00007f9c5622fb6f in TaskManager::TaskGroup::add (this=0x209e6b0, item=0x1c69590) at ../../../libs/taskmanager/taskgroup.cpp:120
#17 0x00007f9c562160fd in TaskManager::AbstractGroupingStrategy::createGroup (this=0x1bfb9c0, items=...) at ../../../libs/taskmanager/abstractgroupingstrategy.cpp:140
#18 0x00007f9c5621e25f in TaskManager::ProgramGroupingStrategy::programGrouping (this=0x1bfb9c0, taskItem=0x1ec9f20, groupItem=0x111b620)
    at ../../../libs/taskmanager/strategies/programgroupingstrategy.cpp:189
#19 0x00007f9c5621ecfb in TaskManager::ProgramGroupingStrategy::handleItem (this=0x1bfb9c0, item=0x1ec9f20) at ../../../libs/taskmanager/strategies/programgroupingstrategy.cpp:156
#20 0x00007f9c56218c6d in TaskManager::GroupManagerPrivate::addTask (this=0x1104cb0, task=...) at ../../../libs/taskmanager/groupmanager.cpp:288
#21 0x00007f9c56219991 in TaskManager::GroupManagerPrivate::actuallyReloadTasks (this=0x1104cb0) at ../../../libs/taskmanager/groupmanager.cpp:155
#22 0x00007f9c5621add2 in TaskManager::GroupManager::qt_metacall (this=0x11193d0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffbbf5bfa0) at ./groupmanager.moc:108
#23 0x00007f9c7286edf2 in QMetaObject::activate (sender=0x1104d18, from_signal_index=<value optimized out>, to_signal_index=4, argv=0x0) at kernel/qobject.cpp:3112
#24 0x00007f9c72869353 in QObject::event (this=0x1104d18, e=0x111b080) at kernel/qobject.cpp:1074
#25 0x00007f9c707e401d in QApplicationPrivate::notify_helper (this=0x8ec900, receiver=0x1104d18, e=0x7fffbbf5c650) at kernel/qapplication.cpp:4065
#26 0x00007f9c707ec07a in QApplication::notify (this=0x8e3ad0, receiver=0x1104d18, e=0x7fffbbf5c650) at kernel/qapplication.cpp:4030
#27 0x00007f9c7143d0db in KApplication::notify (this=0x8e3ad0, receiver=0x1104d18, event=0x7fffbbf5c650) at ../../kdeui/kernel/kapplication.cpp:302
#28 0x00007f9c72859c9c in QCoreApplication::notifyInternal (this=0x8e3ad0, receiver=0x1104d18, event=0x7fffbbf5c650) at kernel/qcoreapplication.cpp:610
#29 0x00007f9c728862c6 in QCoreApplication::sendEvent (this=0x8f0260) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#30 QTimerInfoList::activateTimers (this=0x8f0260) at kernel/qeventdispatcher_unix.cpp:580
#31 0x00007f9c72882658 in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:184
#32 idleTimerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:231
#33 0x00007f9c6f6fe12a in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#34 0x00007f9c6f701988 in ?? () from /lib/libglib-2.0.so.0
#35 0x00007f9c6f701b3c in g_main_context_iteration () from /lib/libglib-2.0.so.0
#36 0x00007f9c7288239c in QEventDispatcherGlib::processEvents (this=0x8ec1f0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:407
#37 0x00007f9c7087af1f in QGuiEventDispatcherGlib::processEvents (this=0x2b, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#38 0x00007f9c72858562 in QEventLoop::processEvents (this=<value optimized out>, flags=...) at kernel/qeventloop.cpp:149
#39 0x00007f9c72858934 in QEventLoop::exec (this=0x7fffbbf5c900, flags=...) at kernel/qeventloop.cpp:201
#40 0x00007f9c7285aba4 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#41 0x00007f9c6797126b in kdemain (argc=1, argv=0x85d7a0) at ../../../../plasma/shells/desktop/main.cpp:50
#42 0x0000000000407264 in launch (argc=1, _name=0x89b558 "/usr/bin/plasma-desktop", args=<value optimized out>, cwd=0x0, envc=0, envs=0x89b578 "", reset_env=false, tty=0x0, avoid_loops=false, 
    startup_id_str=0x40a0ff "0") at ../../kinit/kinit.cpp:677
#43 0x0000000000407a28 in handle_launcher_request (sock=7, who=<value optimized out>) at ../../kinit/kinit.cpp:1169
#44 0x0000000000407fae in handle_requests (waitForPid=0) at ../../kinit/kinit.cpp:1362
#45 0x000000000040863b in main (argc=2, argv=0x7fffbbf5d778, envp=0x7fffbbf5d790) at ../../kinit/kinit.cpp:1793

Reported using DrKonqi