Alo I hate to say it but they aren't officially supported but ATI yet. They do not list it on their website. Have you tried running Windows update to see if there was any kind of prerelease driver? Or checked in the solution center for something?
Personally I would uninstall of the the ATI bundled stuff and start with installing the driver only. ATI Catalystâ„¢ Legacy Display Driver
Have you considered it may be the game? What game is it? Do other games flash like this?
It may be a while too because ATI considered this card legacy...