did you install it to the default location? (program files>ea games>mohaa). I believe this problem occurs when the game is installed in your root directory or something. I also think I've heard people have this problem who have reinstalled (but not uninstalled completely first). a good place to check for an answer is the activision support site since the same issue occured with quake 3 (which is the engine used in mohaa) and fixes for that might be the same. I think the site was
http://activision.custhelp.com