Originally Posted by Jed
Have you tried reinstalling?
Also, what do you mean by "I bought it on the high street"?
"High street" is a British phrase for a shopping area. I think an American like me might think of "shopping mall", but I'm sure they're not identical. The point is, it's a place with legitimate shops, rather than a bazaar where you don't know the shopkeeper and they might not be there next time you come.
BTW, same thing's happening to me, and no, I didn't try reinstalling, mainly because it took so long the first time. I'll resort to it if I have to, but I don't see how it could help, since I only get kicked from some MP games. The CD key I have is clear, and it is entered correctly in the game.