Hi again,
I don't get the problem any more, and I also enabled video acceleration in my second monitor and everything is fine. By the way I am using ccc 10.10 already. Maybe all I needed was a restart

I am not on dual monitor all the time, only when I want to see something in big screen. For an onboard gpu, it covers my needs. I havent tried any games yet but I dont expect much.
Overall I am quite satisfied from this board. It wasnt cheap after all, around 100 euros!
thanks for the help and good night.