I have a problem with my xbox 360 too, when I'm playing Fifa11 it always says Restrictive in red and doesn't let me play online anymore. It was fine up until about a month ago then it doesn't let me.
I have just spoken to the lady who'm I rent my house off, and she said that she has spoken to her IT man Frank, who said that it wouldn't be a good idea to open up another port on the router as it will make her PC vunerable to hackers?? Also Frank said that if I play xbox Fifa2011 online it will slow her PC down at home depending on how many people are online....
Apart from Frank not having a clue on what he is doing, what should I do??