One week ago I (finally) bought Far Cry. Then today I decided to play online (the mane reason I bought the game). But when I enter my serial key, I get a message saying that it is invaled.

I bought the game at a shop. A relatively big one that would never give out illegal copies. If staff could help me I can make a picture of the disc, box and the label with the serial code on it to prove that it's a genuine copy.

It's all in caps and you have to enter the - right?
So it's:
XXX-XXXX-XXXX-XXXX-XXXX.

You do have to enter the "-", but I dont think its case sensitive.