Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.2.85 (KDE 4.2.85 (KDE 4.3 Beta1))
Qt Version: 4.5.1
Operating System: Linux 2.6.28-12-generic x86_64
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
KDE: 4.2.85 from ppa
Distro: Kubuntu 9.04

It happens time and time again that starting some application i.e. firefox crashes plasma.

 -- Backtrace:
Application: Plasma Workspace (plasma-desktop), signal: Segmentation fault
[Current thread is 0 (LWP 4201)]

Thread 2 (Thread 0x7f8729db9950 (LWP 4202)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f8744a2ece9 in QWaitCondition::wait (this=0x27e7a30, mutex=0x27e7a28, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f8747fa95dc in QHostInfoAgent::run (this=0x27e7a10) at kernel/qhostinfo.cpp:260
#3  0x00007f8744a2dd02 in QThreadPrivate::start (arg=0x27e7a10) at thread/qthread_unix.cpp:189
#4  0x00007f87413c23ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#5  0x00007f8743f98fcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f874952a760 (LWP 4201)):
[KCrash Handler]
#5  TaskManager::Task::window (this=0x0) at /build/buildd/kdebase-workspace-4.2.85/libs/taskmanager/task.cpp:356
#6  0x00007f872cab6ade in AbstractTaskItem::timerEvent (this=0x334a420, event=<value optimized out>) at /build/buildd/kdebase-workspace-4.2.85/plasma/applets/tasks/abstracttaskitem.cpp:403
#7  0x00007f8744b26bb3 in QObject::event (this=0x334a420, e=0x33f7290) at kernel/qobject.cpp:1082
#8  0x00007f874583be7b in QGraphicsWidget::event (this=0x334a420, event=0x7fff516f5aa0) at graphicsview/qgraphicswidget.cpp:1340
#9  0x00007f8745220b9d in QApplicationPrivate::notify_helper (this=0x1eebe00, receiver=0x334a420, e=0x7fff516f5aa0) at kernel/qapplication.cpp:4057
#10 0x00007f8745228dea in QApplication::notify (this=0x1ed5b10, receiver=0x334a420, e=0x7fff516f5aa0) at kernel/qapplication.cpp:4022
#11 0x00007f87478e51ab in KApplication::notify (this=0x1ed5b10, receiver=0x334a420, event=0x7fff516f5aa0) at /build/buildd/kde4libs-4.2.85/kdeui/kernel/kapplication.cpp:307
#12 0x00007f8744b16dfc in QCoreApplication::notifyInternal (this=0x1ed5b10, receiver=0x334a420, event=0x7fff516f5aa0) at kernel/qcoreapplication.cpp:610
#13 0x00007f8744b43eb6 in QTimerInfoList::activateTimers (this=0x1eef6d0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#14 0x00007f8744b405cd in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:164
#15 0x00007f873f79220a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#16 0x00007f873f7958e0 in ?? () from /usr/lib/libglib-2.0.so.0
#17 0x00007f873f795a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#18 0x00007f8744b4052f in QEventDispatcherGlib::processEvents (this=0x1ebd5f0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:324
#19 0x00007f87452b970f in QGuiEventDispatcherGlib::processEvents (this=0x0, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#20 0x00007f8744b156a2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 1366252816}) at kernel/qeventloop.cpp:149
#21 0x00007f8744b15a6d in QEventLoop::exec (this=0x7fff516f5d50, flags={i = 1366252896}) at kernel/qeventloop.cpp:200
#22 0x00007f8744b17d34 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#23 0x00007f874928f29b in kdemain (argc=1, argv=0x7fff516f6058) at /build/buildd/kdebase-workspace-4.2.85/plasma/shells/desktop/main.cpp:50
#24 0x00007f8743ed15a6 in __libc_start_main (main=0x400890 <main>, argc=1, ubp_av=0x7fff516f6058, init=0x4008c0 <__libc_csu_init>, fini=<value optimized out>, rtld_fini=<value optimized out>, 
    stack_end=0x7fff516f6048) at libc-start.c:220
#25 0x00000000004007c9 in _start () at ../sysdeps/x86_64/elf/start.S:113