Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.2.96 (KDE 4.2.96 (KDE 4.3 RC2))
Qt Version: 4.5.2
Operating System: Linux 2.6.29-ARCH i686

What I was doing when the application crashed:
i dragged a window (on desktop 2) to the pager to get it on desktop 3. normally i had no crashes when i made this operation. i dragged a skype window (chat window) back to desktop 3 (there is the skype main window). the taskmanager grouped the windows and strangely split up the taskmanager in two rows. then i switched back to desktop 3 and i got the crash.

 -- Backtrace:
Application: Plasma Workspace (kdeinit4), signal: Segmentation fault
[Current thread is 0 (LWP 3127)]

Thread 2 (Thread 0xa8343b70 (LWP 3135)):
#0  0xb806c424 in __kernel_vsyscall ()
#1  0xb7e09bc5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb7e68037 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#3  0xb662aaa2 in ?? () from /usr/lib/libQtNetwork.so.4
#4  0xb7e67022 in ?? () from /usr/lib/libQtCore.so.4
#5  0xb7e0568c in start_thread () from /lib/libpthread.so.0
#6  0xb68a7e2e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb5e9b710 (LWP 3127)):
[KCrash Handler]
#6  0xa948e2dc in AbstractTaskItem::basicPreferredSize () from /usr/lib/kde4/plasma_applet_tasks.so
#7  0xa948a28b in TaskItemLayout::preferredColumns () from /usr/lib/kde4/plasma_applet_tasks.so
#8  0xa948afca in TaskItemLayout::gridLayoutSize () from /usr/lib/kde4/plasma_applet_tasks.so
#9  0xa948b08b in TaskItemLayout::layoutItems () from /usr/lib/kde4/plasma_applet_tasks.so
#10 0xa948bbba in TaskItemLayout::insert () from /usr/lib/kde4/plasma_applet_tasks.so
#11 0xa948bd9f in TaskItemLayout::addTaskItem () from /usr/lib/kde4/plasma_applet_tasks.so
#12 0xa9498222 in TaskGroupItem::itemAdded () from /usr/lib/kde4/plasma_applet_tasks.so
#13 0xa94991a7 in TaskGroupItem::qt_metacall () from /usr/lib/kde4/plasma_applet_tasks.so
#14 0xb7f6b8bc in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#15 0xb7f6c4f2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#16 0xa94cd843 in TaskManager::TaskGroup::itemAdded () from /usr/lib/libtaskmanager.so.4
#17 0xa94ce295 in TaskManager::TaskGroup::add () from /usr/lib/libtaskmanager.so.4
#18 0xa94b249e in TaskManager::AbstractGroupingStrategy::closeGroup () from /usr/lib/libtaskmanager.so.4
#19 0xa94b9dfd in TaskManager::ProgramGroupingStrategy::checkGroup () from /usr/lib/libtaskmanager.so.4
#20 0xa94baad1 in TaskManager::ProgramGroupingStrategy::qt_metacall () from /usr/lib/libtaskmanager.so.4
#21 0xb7f6b8bc in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#22 0xb7f6c4f2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#23 0xa94cd7f3 in TaskManager::TaskGroup::itemRemoved () from /usr/lib/libtaskmanager.so.4
#24 0xa94ce01b in TaskManager::TaskGroup::remove () from /usr/lib/libtaskmanager.so.4
#25 0xa94b56ad in TaskManager::GroupManagerPrivate::removeTask () from /usr/lib/libtaskmanager.so.4
#26 0xa94b5b83 in TaskManager::GroupManagerPrivate::actuallyReloadTasks () from /usr/lib/libtaskmanager.so.4
#27 0xa94b72ee in TaskManager::GroupManager::qt_metacall () from /usr/lib/libtaskmanager.so.4
#28 0xb7f6b8bc in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#29 0xb7f6c4f2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#30 0xb7fa5957 in QTimer::timeout () from /usr/lib/libQtCore.so.4
#31 0xb7f70f6e in QTimer::timerEvent () from /usr/lib/libQtCore.so.4
#32 0xb7f65a6f in QObject::event () from /usr/lib/libQtCore.so.4
#33 0xb6b32674 in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#34 0xb6b39d5c in QApplication::notify () from /usr/lib/libQtGui.so.4
#35 0xb7572f0a in KApplication::notify () from /usr/lib/libkdeui.so.5
#36 0xb7f55edb in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#37 0xb7f8364e in ?? () from /usr/lib/libQtCore.so.4
#38 0xb7f80630 in ?? () from /usr/lib/libQtCore.so.4
#39 0xb673cd98 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#40 0xb67403e0 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#41 0xb6740513 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#42 0xb7f8057c in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#43 0xb6bd0475 in ?? () from /usr/lib/libQtGui.so.4
#44 0xb7f54489 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#45 0xb7f548da in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#46 0xb7f56d4f in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#47 0xb6b324f7 in QApplication::exec () from /usr/lib/libQtGui.so.4
#48 0xb4980b0d in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#49 0x0804de42 in _start ()

Reported using DrKonqi