Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.2.90 (KDE 4.2.90 (KDE 4.3 Beta2))
Qt Version: 4.5.0
Operating System: Linux 2.6.28-12-generic x86_64
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
I updated to 4.3beta, and after that my desktop settings and plasma widgets were gone. So far no problem (can occur on an update).
Then i tried to rearrange my widgets, and when i removed the weather forecast widget, plasma crashed with the attached backtrace.

 -- Backtrace:
Application: Plasma Workspace (kdeinit), signal: Segmentation fault
[Current thread is 0 (LWP 1522)]

Thread 2 (Thread 0x7f6136bae950 (LWP 1529)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f6156316939 in QWaitCondition::wait (this=0x2d994c0, mutex=0x2d994b8, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f61551934cc in QHostInfoAgent::run (this=0x2d994a0) at kernel/qhostinfo.cpp:260
#3  0x00007f6156315952 in QThreadPrivate::start (arg=0x2d994a0) at thread/qthread_unix.cpp:189
#4  0x00007f61521973ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#5  0x00007f6152d7bfcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f61568d9750 (LWP 1522)):
[KCrash Handler]
#5  0x0000000000000021 in ?? ()
#6  0x00007f6153fa120a in ~QGraphicsWidget (this=0x294f9f0) at graphicsview/qgraphicswidget.cpp:284
#7  0x00007f6153f5f297 in ~QGraphicsItem (this=0x37f18e0) at graphicsview/qgraphicsitem.cpp:867
#8  0x00007f6153fa052a in ~QGraphicsWidget (this=0x37f18d0) at graphicsview/qgraphicswidget.cpp:299
#9  0x00007f614dcb1659 in ~Applet (this=0x37f18d0) at /build/buildd/kde4libs-4.2.90/plasma/applet.cpp:187
#10 0x00007f612dd2f3a8 in ?? () from /usr/lib/kde4/plasma_applet_weather.so
#11 0x00007f615640e865 in QObject::event (this=0x37f18d0, e=0x0) at kernel/qobject.cpp:1101
#12 0x00007f6153f9d74b in QGraphicsWidget::event (this=0x37f18d0, event=0x277f1c0) at graphicsview/qgraphicswidget.cpp:1317
#13 0x00007f615398878d in QApplicationPrivate::notify_helper (this=0x254cfa0, receiver=0x37f18d0, e=0x277f1c0) at kernel/qapplication.cpp:4084
#14 0x00007f615399097a in QApplication::notify (this=0x250dc30, receiver=0x37f18d0, e=0x277f1c0) at kernel/qapplication.cpp:4049
#15 0x00007f6154acb06b in KApplication::notify (this=0x250dc30, receiver=0x37f18d0, event=0x277f1c0) at /build/buildd/kde4libs-4.2.90/kdeui/kernel/kapplication.cpp:302
#16 0x00007f61563fe75c in QCoreApplication::notifyInternal (this=0x250dc30, receiver=0x37f18d0, event=0x277f1c0) at kernel/qcoreapplication.cpp:602
#17 0x00007f61563ff3ca in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x24bc100) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#18 0x00007f61564281e3 in postEventSourceDispatch (s=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#19 0x00007f61523e620a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#20 0x00007f61523e98e0 in ?? () from /usr/lib/libglib-2.0.so.0
#21 0x00007f61523e9a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#22 0x00007f6156427e6f in QEventDispatcherGlib::processEvents (this=0x254cc40, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:323
#23 0x00007f6153a20bef in QGuiEventDispatcherGlib::processEvents (this=0x37f6f00, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#24 0x00007f61563fd002 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 1586574368}) at kernel/qeventloop.cpp:149
#25 0x00007f61563fd3cd in QEventLoop::exec (this=0x7fff5e913460, flags={i = 1586574448}) at kernel/qeventloop.cpp:200
#26 0x00007f61563ff694 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#27 0x00007f614a2d67eb in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#28 0x000000000040714e in launch (argc=1, _name=0x2500388 "/usr/bin/plasma-desktop", args=<value optimized out>, cwd=0x0, envc=0, envs=0x25003a8 "", reset_env=false, tty=0x0, avoid_loops=false, 
    startup_id_str=0x40a308 "0") at /build/buildd/kde4libs-4.2.90/kinit/kinit.cpp:671
#29 0x0000000000407978 in handle_launcher_request (sock=7, who=<value optimized out>) at /build/buildd/kde4libs-4.2.90/kinit/kinit.cpp:1163
#30 0x0000000000407f25 in handle_requests (waitForPid=0) at /build/buildd/kde4libs-4.2.90/kinit/kinit.cpp:1356
#31 0x0000000000408a66 in main (argc=2, argv=0x7fff5e9142f8, envp=0x7fff5e914310) at /build/buildd/kde4libs-4.2.90/kinit/kinit.cpp:1783

Reported using DrKonqi