Sorry I don't speak German, but I understand what you mean. Hope you understand English
If you have forced AA and AF in your ATI control panel, set them to "application managed". I also have an ATI and fooling around with the 3D settings there made this go away for me. In the ATI panel, I have VSync on (Vertical refresh) and adaptive AA on, but I don't think this has much to do with this.
