Comment 31 for bug 351990

I can confirm this behaviour, system locks up or screen goes completely dark with a hard reset as the only option left.
This is on a Laptop with an Ati Radeon 9600 Mobility M10 (RV350) card using the radeon driver and kwin's compositing effects enabled.

The lock-ups occur when opening random applications, so far it happened to me while opening kwallet, login-manager, kate, kpackagekit and others.

Also, X sometimes uses up to 50% of the cpu-time.