Video artifacts

Hello,

I am getting some weird artifacts lately.
Some sort of thick bars are forming, where the colors are slightly distorted, which reset every few seconds.
I don't know how to explain it better ..
It can be seen in this photo: (most visible in the center)


This doesn't happen to all videos, but the same ones work normal on Vlc, Totem, etc. (tested on another computer)
I'm using https://launchpad.net/~wsnipex/+archive/xbmc-xvba with the latest fglrx/catalyst driver (13.1) on Ubuntu Quantal.