Version:            (using KDE 4.3.1)
OS:                Linux
Installed from:    Fedora RPMs

plasma-desktop crashes when switching between desktops

How to reproduce:
Unfortunately, I don't have exact steps to reproduce. However crashes now occurs quite regularly when I switch several times between desktops.

Please see attached backtrace:
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Application: Plasma Workspace (plasma-desktop), signal: Segmentation fault
[Current thread is 1 (Thread 0x7f8cd4064820 (LWP 2099))]

Thread 2 (Thread 0x7f8cbd3fc910 (LWP 2100)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x0000003289a5adfb 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  0x000000328a6818e4 in QHostInfoAgent::run (this=0x2a83690) at kernel/qhostinfo.cpp:260
#4  0x0000003289a59d45 in QThreadPrivate::start (arg=0x2a83690) at thread/qthread_unix.cpp:188
#5  0x000000327de0686a in start_thread (arg=<value optimized out>) at pthread_create.c:297
#6  0x000000327d2de3bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#7  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f8cd4064820 (LWP 2099)):
[KCrash Handler]
#5  Tasks::itemTopMargin (this=<value optimized out>) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/tasks.h:92
#6  AbstractTaskItem::basicPreferredSize (this=<value optimized out>) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/abstracttaskitem.cpp:99
#7  0x00007f8cc2082155 in TaskItemLayout::preferredColumns (this=0x2aa8930) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskitemlayout.cpp:206
#8  0x00007f8cc2082e3d in TaskItemLayout::gridLayoutSize (this=0x2aa8930) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskitemlayout.cpp:222
#9  0x00007f8cc2082ecb in TaskItemLayout::layoutItems (this=0x0) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskitemlayout.cpp:245
#10 0x00007f8cc208395f in TaskItemLayout::insert (this=0x2aa8930, index=<value optimized out>, item=0x3ad8780) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskitemlayout.cpp:125
#11 0x00007f8cc2083b30 in TaskItemLayout::addTaskItem (this=0x2aa8930, item=0x3ad8780) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskitemlayout.cpp:82
#12 0x00007f8cc208f848 in TaskGroupItem::itemAdded (this=0x2aa4390, groupableItem=0x3a3d0f0) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/applets/tasks/taskgroupitem.cpp:477
#13 0x00007f8cc208fe94 in TaskGroupItem::qt_metacall (this=0x2aa4390, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffc715ff60)
    at /usr/src/debug/kdebase-workspace-4.3.1/x86_64-redhat-linux-gnu/plasma/applets/tasks/taskgroupitem.moc:113
#14 0x0000003289b547dc in QMetaObject::activate (sender=0x2aa3db0, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x327d569e98) at kernel/qobject.cpp:3113
#15 0x0000003dd3a30fbf in TaskManager::TaskGroup::itemAdded (this=0x0, _t1=0x3a3d0f0) at /usr/src/debug/kdebase-workspace-4.3.1/x86_64-redhat-linux-gnu/libs/taskmanager/taskgroup.moc:139
#16 0x0000003dd3a3189b in TaskManager::TaskGroup::add (this=0x2aa3db0, item=0x3a3d0f0) at /usr/src/debug/kdebase-workspace-4.3.1/libs/taskmanager/taskgroup.cpp:138
#17 0x0000003dd3a20dbd in TaskManager::ProgramGroupingStrategy::handleItem (this=0x3a8ba50, item=0x3a3d0f0)
    at /usr/src/debug/kdebase-workspace-4.3.1/libs/taskmanager/strategies/programgroupingstrategy.cpp:154
#18 0x0000003dd3a1ad1a in TaskManager::GroupManagerPrivate::addTask (this=0x2aa0100, task={d = 0x2a9cd00}) at /usr/src/debug/kdebase-workspace-4.3.1/libs/taskmanager/groupmanager.cpp:288
#19 0x0000003dd3a1b65b in TaskManager::GroupManagerPrivate::actuallyReloadTasks (this=0x2aa0100) at /usr/src/debug/kdebase-workspace-4.3.1/libs/taskmanager/groupmanager.cpp:155
#20 0x0000003dd3a1ce89 in TaskManager::GroupManager::qt_metacall (this=0x29d3a40, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffc7160230)
    at /usr/src/debug/kdebase-workspace-4.3.1/x86_64-redhat-linux-gnu/libs/taskmanager/groupmanager.moc:108
#21 0x0000003289b547dc in QMetaObject::activate (sender=0x2aa0168, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x327d569e98) at kernel/qobject.cpp:3113
#22 0x0000003289b4e7de in QObject::event (this=0x2aa0168, e=0x385bf60) at kernel/qobject.cpp:1075
#23 0x000000328ab8f69c in QApplicationPrivate::notify_helper (this=0x262a470, receiver=0x2aa0168, e=0x7fffc7160830) at kernel/qapplication.cpp:4056
#24 0x000000328ab968fe in QApplication::notify (this=0x2618a60, receiver=0x2aa0168, e=0x7fffc7160830) at kernel/qapplication.cpp:4021
#25 0x000000328cc11b56 in KApplication::notify (this=0x2618a60, receiver=0x2aa0168, event=0x7fffc7160830) at /usr/src/debug/kdelibs-4.3.1/kdeui/kernel/kapplication.cpp:302
#26 0x0000003289b3f59c in QCoreApplication::notifyInternal (this=0x2618a60, receiver=0x2aa0168, event=0x7fffc7160830) at kernel/qcoreapplication.cpp:610
#27 0x0000003289b69fc2 in QCoreApplication::sendEvent (event=<value optimized out>, receiver=<value optimized out>) at kernel/qcoreapplication.h:213
#28 QTimerInfoList::activateTimers (event=<value optimized out>, receiver=<value optimized out>) at kernel/qeventdispatcher_unix.cpp:572
#29 0x0000003289b679ed in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:165
#30 0x000000327fa3790e in g_main_dispatch (context=<value optimized out>) at gmain.c:1824
#31 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2377
#32 0x000000327fa3b0e8 in g_main_context_iterate (context=0x262cd20, block=<value optimized out>, dispatch=<value optimized out>, self=<value optimized out>) at gmain.c:2455
#33 0x000000327fa3b20a in IA__g_main_context_iteration (context=0x262cd20, may_block=1) at gmain.c:2518
#34 0x0000003289b67936 in QEventDispatcherGlib::processEvents (this=0x2600810, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#35 0x000000328ac21f8e in QGuiEventDispatcherGlib::processEvents (this=0x0, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#36 0x0000003289b3ded2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 36}) at kernel/qeventloop.cpp:149
#37 0x0000003289b3e2a4 in QEventLoop::exec (this=0x7fffc7160ad0, flags={i = 0}) at kernel/qeventloop.cpp:201
#38 0x0000003289b40439 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#39 0x0000003dd2a3af4f in kdemain (argc=<value optimized out>, argv=<value optimized out>) at /usr/src/debug/kdebase-workspace-4.3.1/plasma/shells/desktop/main.cpp:50
#40 0x000000327d21ea2d in __libc_start_main (main=<value optimized out>, argc=<value optimized out>, ubp_av=<value optimized out>, init=<value optimized out>, fini=<value optimized out>, 
    rtld_fini=<value optimized out>, stack_end=0x7fffc7160dd8) at libc-start.c:220
#41 0x0000000000400779 in _start ()
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