Created attachment 115164 [details]
dmesg

I experience random lockups of the screen. The screen goes black then sometimes
the image is back but frozen, sometimes it stays black. I can't do anything but
a hard reset. It happens randomly when using KDE4 desktop and common
applications (eclipse, firefox etc.). I did not notice any correlation with any
particular usage pattern or application. I have DPM enabled.
I attach the significant part of journaclt log recovered after reboot.

Hardware: Mobility Radeon HD3470 (RV620)
System: ArchLinux x86_64
Packages: linux 3.19.4  with ck patchset, xf86-video-ati 1:7.5.0, mesa 10.5.3