What operating system are you running?
It seems this problem is becoming a common issue.
do you have a hard copy or did you legally download it? Some people are having trouble with the downloaded version.
Also if you haven’t already tried;
Re-install the game with uac turned off
Run the game as administrator
Also, if you’re using vista, login to the 'administrator' account and try run the game from there. Search Google on how to achieve the administrator account.