Oke, 1st thing to do:
Restart the computer (if you didn't do that so far) and try.
If that fais, delete folder "cache" over here: C:\Users\Nevermind.for.phone.numer.I.still.like.you\AppData\Roaming\Sports Interactive\Football Manager 2011\cache

(this is Win 7 path, ignore "roaming" if you have XP or anything else.
Then start FM and check if it's working.
If that fails too, type "dxdiag" in "Run" and open it. Check the name of your grahpic card.
Then find the latest driver on site of the manufacters, download it, install it and try.
