Created attachment 24212 [details]
Foto of the screen after the crash
After about ~4hours of use (~8500 drm mm objects, 700mb SHR memory), when I enabled kwin's XRender based composition manager the system crashed hard.
I was not able to log into the machine with ssh, and the audio-buffer was not filled anymore.
The screen showed some strange flicker, as shown in the screenshot attached.
This is the second time this problem has happend to me.
Created attachment 24213 [details]
not sure if this is related to bug#21398
Clemens, how about this with recent releases?
haven't seen it for ages, guess its fixed.