Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.3.4 (KDE 4.3.4)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-15-generic i686
Distribution: Ubuntu 9.10

What I was doing when the application crashed:
I think the problem is with the task manager applet of the panel. If this is true ¿why the entire plasma crashes if a widget crashed?
Any way. I've notice that when I switch from one workspace with no windows to another with windows (I have configure it to only show windows from the current WS) when the system is busy, the task manager applet shows the buttons in a extrange way I will attach an screenshot of one of them. some times as if it was configured to «force row settings», other times it lets a space at the begining, as if there was a button there but no visible. Just as it... no button actually.

 -- Backtrace:
Application: Plasma Workspace (kdeinit4), signal: Segmentation fault
[Current thread is 1 (Thread 0xb77fc700 (LWP 1527))]

Thread 2 (Thread 0xac6a8b70 (LWP 1528)):
#0  0x00ff2422 in __kernel_vsyscall ()
#1  0x004bbe15 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0x00d4478d in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0x00804e67 in QWaitConditionPrivate::wait (this=0x9300a18, mutex=0x9300a14, time=4294967295) at thread/qwaitcondition_unix.cpp:87
#4  QWaitCondition::wait (this=0x9300a18, mutex=0x9300a14, time=4294967295) at thread/qwaitcondition_unix.cpp:159
#5  0x00e29922 in QHostInfoAgent::run (this=0x9300a08) at kernel/qhostinfo.cpp:260
#6  0x00803e32 in QThreadPrivate::start (arg=0x9300a08) at thread/qthread_unix.cpp:188
#7  0x004b780e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#8  0x00d377ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb77fc700 (LWP 1527)):
[KCrash Handler]
#6  0x016359e7 in TaskItemLayout::layoutItems (this=0x91f8b90) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:325
#7  0x016368aa in TaskItemLayout::remove (this=0x91f8b90, item=0x9a71d70) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:141
#8  0x01636aec in TaskItemLayout::removeTaskItem (this=0x91f8b90, item=0x9a71d70) at ../../../../plasma/applets/tasks/taskitemlayout.cpp:93
#9  0x0164394f in TaskGroupItem::itemPositionChanged (this=0x920b030, item=0x99a6040) at ../../../../plasma/applets/tasks/taskgroupitem.cpp:882
#10 0x01643dff in TaskGroupItem::qt_metacall (this=0x920b030, _c=QMetaObject::InvokeMetaMethod, _id=33, _a=0xbf876658) at ./taskgroupitem.moc:116
#11 0x0090a263 in QMetaObject::activate (sender=0x91f96f8, from_signal_index=24, to_signal_index=24, argv=0xbf876658) at kernel/qobject.cpp:3113
#12 0x0090aec2 in QMetaObject::activate (sender=0x91f96f8, m=0x1683bf4, local_signal_index=3, argv=0xbf876658) at kernel/qobject.cpp:3187
#13 0x01675353 in TaskManager::TaskGroup::itemPositionChanged (this=0x91f96f8, _t1=0x99a6040) at ./taskgroup.moc:165
#14 0x01677913 in TaskManager::TaskGroup::moveItem (this=0x91f96f8, oldIndex=4, newIndex=0) at ../../../libs/taskmanager/taskgroup.cpp:568
#15 0x0165bbd1 in TaskManager::AbstractSortingStrategy::check (this=0x921e1d0, itemToCheck=0x0) at ../../../libs/taskmanager/abstractsortingstrategy.cpp:149
#16 0x0165bf9b in TaskManager::AbstractSortingStrategy::qt_metacall (this=0x921e1d0, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbf87681c) at ./abstractsortingstrategy.moc:74
#17 0x016608b2 in TaskManager::AlphaSortingStrategy::qt_metacall (this=0x921e1d0, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbf87681c) at ./alphasortingstrategy.moc:58
#18 0x0090a263 in QMetaObject::activate (sender=0x99a6040, from_signal_index=21, to_signal_index=21, argv=0x0) at kernel/qobject.cpp:3113
#19 0x0090aec2 in QMetaObject::activate (sender=0x99a6040, m=0x1683cdc, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3187
#20 0x01677b27 in TaskManager::TaskItem::gotTaskPointer (this=0x99a6040) at ./taskitem.moc:116
#21 0x0167833c in TaskManager::TaskItem::setTaskPointer (this=0x99a6040, task=) at ../../../libs/taskmanager/taskitem.cpp:99
#22 0x0165d2a2 in TaskManager::GroupManagerPrivate::addTask (this=0x91fbb58, task=) at ../../../libs/taskmanager/groupmanager.cpp:268
#23 0x0165f343 in TaskManager::GroupManager::qt_metacall (this=0x8bd8770, _c=QMetaObject::InvokeMetaMethod, _id=10, _a=0xbf876a88) at ./groupmanager.moc:103
#24 0x0090a263 in QMetaObject::activate (sender=0x91fbbd0, from_signal_index=4, to_signal_index=4, argv=0xbf876a88) at kernel/qobject.cpp:3113
#25 0x0090aec2 in QMetaObject::activate (sender=0x91fbbd0, m=0x1683dbc, local_signal_index=0, argv=0xbf876a88) at kernel/qobject.cpp:3187
#26 0x01678e83 in TaskManager::TaskManager::taskAdded (this=0x91fbbd0, _t1=...) at ./taskmanager.moc:155
#27 0x0167b063 in TaskManager::TaskManager::windowAdded (this=0x91fbbd0, w=23068716) at ../../../libs/taskmanager/taskmanager.cpp:262
#28 0x0167c4df in TaskManager::TaskManager::qt_metacall (this=0x91fbbd0, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbf876c58) at ./taskmanager.moc:109
#29 0x0090a263 in QMetaObject::activate (sender=0x8df4620, from_signal_index=5, to_signal_index=5, argv=0xbf876c58) at kernel/qobject.cpp:3113
#30 0x0090aec2 in QMetaObject::activate (sender=0x8df4620, m=0x137e26c, local_signal_index=1, argv=0xbf876c58) at kernel/qobject.cpp:3187
#31 0x013153d3 in KWindowSystem::windowAdded (this=0x8df4620, _t1=23068716) at ./kwindowsystem.moc:120
#32 0x01318496 in KWindowSystemPrivate::addClient (this=0x8dfca60, w=23068716) at ../../kdeui/windowmanagement/kwindowsystem_x11.cpp:229
#33 0x01326b27 in NETRootInfo::update (this=0x8dfca74, dirty_props=0xbf876e08) at ../../kdeui/windowmanagement/netwm.cpp:2186
#34 0x01327667 in NETRootInfo::event (this=0x8dfca74, event=<value optimized out>, properties=0xbf876ef4, properties_size=5) at ../../kdeui/windowmanagement/netwm.cpp:2058
#35 0x01318881 in KWindowSystemPrivate::x11Event (this=0x8dfca60, ev=0xbf8784fc) at ../../kdeui/windowmanagement/kwindowsystem_x11.cpp:136
#36 0x011c5536 in KAppX11HackWidget::publicx11Event (this=0x8b74af8, _event=0xbf8784fc) at ../../kdeui/kernel/kapplication.cpp:911
#37 KApplication::x11EventFilter (this=0x8b74af8, _event=0xbf8784fc) at ../../kdeui/kernel/kapplication.cpp:961
#38 0x0495371a in PlasmaApp::x11EventFilter (this=0x8b74af8, event=0xbf8784fc) at ../../../../plasma/shells/desktop/plasmaapp.cpp:490
#39 0x03711d70 in qt_x11EventFilter (ev=0xbf8784fc) at kernel/qapplication_x11.cpp:375
#40 0x03723375 in QApplication::x11ProcessEvent (this=0x8b74af8, event=0xbf8784fc) at kernel/qapplication_x11.cpp:3271
#41 0x03751502 in x11EventSourceDispatch (s=0x8b9e568, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#42 0x00733e78 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#43 0x00737720 in ?? () from /lib/libglib-2.0.so.0
#44 0x00737853 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#45 0x0091f02c in QEventDispatcherGlib::processEvents (this=0x8b9b738, flags=...) at kernel/qeventdispatcher_glib.cpp:327
#46 0x03750be5 in QGuiEventDispatcherGlib::processEvents (this=0x8b9b738, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#47 0x008f2c79 in QEventLoop::processEvents (this=0xbf8787f4, flags=) at kernel/qeventloop.cpp:149
#48 0x008f30ca in QEventLoop::exec (this=0xbf8787f4, flags=...) at kernel/qeventloop.cpp:201
#49 0x008f553f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#50 0x036afdd7 in QApplication::exec () at kernel/qapplication.cpp:3525
#51 0x0493d80d in kdemain (argc=1, argv=0x8b221e8) at ../../../../plasma/shells/desktop/main.cpp:50
#52 0x0804dde1 in launch (argc=<value optimized out>, _name=<value optimized out>, args=<value optimized out>, cwd=0x0, envc=0, envs=0x8b3c090 "", reset_env=false, tty=0x0, avoid_loops=false, 
    startup_id_str=0x80511a5 "0") at ../../kinit/kinit.cpp:677
#53 0x0804ea35 in handle_launcher_request (sock=<value optimized out>, who=<value optimized out>) at ../../kinit/kinit.cpp:1169
#54 0x0804eeac in handle_requests (waitForPid=<value optimized out>) at ../../kinit/kinit.cpp:1362
#55 0x0804fbaf in main (argc=2, argv=0xbf879054, envp=0xbf879060) at ../../kinit/kinit.cpp:1793

Reported using DrKonqi