Do these:
1) Download
Driver Sweeper and install it. Do not run it yet.
2) Uninstall the AMD drivers and all of their components.
3) Now run Driver Sweeper. Select all ATI, AMD, NVIDIA traces and if it founds something delete them all.
4) Reboot your system and then download this(Catalyst 11.6, do not use the beta 11.7 or something else - 11.6 should be perfect):
http://sites.amd.com/us/game/downloads/P...n7-64.aspx
5) After installation reboot your system again. Make sure that in device manager your AMD card appears and try launching the game again.