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: 4.5.1
Operating System: Linux 2.6.28-13-generic x86_64
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
Plasma crash after unlock screen or when many windows are open.

There is a hight probability of plasma to crash when there are many windows open.

The desktop is unstable, mouse slow when unlocking screen after a period of inactivity.

The screensaver was running and was glmatrix.

 -- Backtrace:
Application: Plasma Workspace (kdeinit), signal: Segmentation fault
[Current thread is 0 (LWP 14460)]

Thread 2 (Thread 0x7f8361aaa950 (LWP 14463)):
#0  0x00007f837e8602e9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007f838298cce9 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#2  0x00007f83818185dc in ?? () from /usr/lib/libQtNetwork.so.4
#3  0x00007f838298bd02 in ?? () from /usr/lib/libQtCore.so.4
#4  0x00007f837e85c3ba in start_thread () from /lib/libpthread.so.0
#5  0x00007f837f440fcd in clone () from /lib/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f8382f4f750 (LWP 14460)):
[KCrash Handler]
#5  0x00007f837f3dbc40 in strlen () from /lib/libc.so.6
#6  0x00007f8382a7d9f8 in QMetaObject::invokeMethod () from /usr/lib/libQtCore.so.4
#7  0x00007f837a36c033 in Plasma::Animator::timerEvent () from /usr/lib/libplasma.so.3
#8  0x00007f8382a84bb3 in QObject::event () from /usr/lib/libQtCore.so.4
#9  0x00007f8380017b9d in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#10 0x00007f838001fdea in QApplication::notify () from /usr/lib/libQtGui.so.4
#11 0x00007f838115406b in KApplication::notify () from /usr/lib/libkdeui.so.5
#12 0x00007f8382a74dfc in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#13 0x00007f8382aa1eb6 in ?? () from /usr/lib/libQtCore.so.4
#14 0x00007f8382a9e5cd in ?? () from /usr/lib/libQtCore.so.4
#15 0x00007f837eaab20a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#16 0x00007f837eaae8e0 in ?? () from /usr/lib/libglib-2.0.so.0
#17 0x00007f837eaaea7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#18 0x00007f8382a9e52f in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#19 0x00007f83800b070f in ?? () from /usr/lib/libQtGui.so.4
#20 0x00007f8382a736a2 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#21 0x00007f8382a73a6d in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#22 0x00007f8382a75d34 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#23 0x00007f83769a37eb in kdemain () from /usr/lib/libkdeinit4_plasma-desktop.so
#24 0x000000000040714e in _start ()

Reported using DrKonqi