Application that crashed: plasma-desktop
Version of the application: 0.3
KDE Version: 4.2.95 (KDE 4.2.95 (KDE 4.3 RC1))
Qt Version: 4.5.0
Operating System: Linux 2.6.28-13-generic i686
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
Crash when I lock/unlock the widgets...

 -- Backtrace:
Application: Plasma Workspace (kdeinit4), signal: Segmentation fault
[Current thread is 0 (LWP 3778)]

Thread 2 (Thread 0xa811cb90 (LWP 3785)):
#0  0xb7f2d430 in __kernel_vsyscall ()
#1  0xb63d70e5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb65d72ed in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0xb7d2a9b2 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#4  0xb7666152 in ?? () from /usr/lib/libQtNetwork.so.4
#5  0xb7d2996e in ?? () from /usr/lib/libQtCore.so.4
#6  0xb63d34ff in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0xb65c849e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb5f15970 (LWP 3778)):
[KCrash Handler]
#6  0xb6edba9a in QGraphicsItem::isWidget () from /usr/lib/libQtGui.so.4
#7  0xb6f11b27 in QGraphicsScene::event () from /usr/lib/libQtGui.so.4
#8  0xb68ade9c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#9  0xb68b619e in QApplication::notify () from /usr/lib/libQtGui.so.4
#10 0xb73e83dd in KApplication::notify () from /usr/lib/libkdeui.so.5
#11 0xb7e1da3b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#12 0xb6f221c5 in QGraphicsView::viewportEvent () from /usr/lib/libQtGui.so.4
#13 0xb6d80f55 in ?? () from /usr/lib/libQtGui.so.4
#14 0xb7e1cc5a in QCoreApplicationPrivate::sendThroughObjectEventFilters () from /usr/lib/libQtCore.so.4
#15 0xb68ade7a in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#16 0xb68b6282 in QApplication::notify () from /usr/lib/libQtGui.so.4
#17 0xb73e83dd in KApplication::notify () from /usr/lib/libkdeui.so.5
#18 0xb7e1da3b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#19 0xb690461d in QWidget::event () from /usr/lib/libQtGui.so.4
#20 0xb6cde993 in QFrame::event () from /usr/lib/libQtGui.so.4
#21 0xb6d7f44d in QAbstractScrollArea::event () from /usr/lib/libQtGui.so.4
#22 0xb6f21ff6 in QGraphicsView::event () from /usr/lib/libQtGui.so.4
#23 0xb68ade9c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#24 0xb68b6282 in QApplication::notify () from /usr/lib/libQtGui.so.4
#25 0xb73e83dd in KApplication::notify () from /usr/lib/libkdeui.so.5
#26 0xb7e1da3b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#27 0xb68b4d9e in QApplication::setActiveWindow () from /usr/lib/libQtGui.so.4
#28 0xb692456c in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#29 0xb694fc6a in ?? () from /usr/lib/libQtGui.so.4
#30 0xb6420788 in IA__g_main_context_dispatch (context=0x997f098) at gmain.c:1814
#31 0xb6423ceb in g_main_context_iterate (context=0x997f098, block=1, dispatch=1, self=0x997ca18) at gmain.c:2448
#32 0xb6423e68 in IA__g_main_context_iteration (context=0x997f098, may_block=1) at gmain.c:2511
#33 0xb7e49438 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#34 0xb694f365 in ?? () from /usr/lib/libQtGui.so.4
#35 0xb7e1c06a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#36 0xb7e1c4aa in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#37 0xb7e1e959 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#38 0xb68add17 in QApplication::exec () from /usr/lib/libQtGui.so.4
#39 0xb3b10510 in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#40 0x0804e1c0 in _start ()

Reported using DrKonqi