I have 2 Radaeon 6900 Series, I have played the new Hitman on max settings with no problem... But when I installed the Beta driver and went back to the old original drivers. Now it is all glitchy... I even have Cross Fire enabled.
Ok, perhaps you might need to remove the graphic driver completely, i.e. using so named driver and/or registry cleaners. After that, please try to install the graphics driver version you need.