my personal experience with this game trying to get on the sever to play online has had me in fits of anger, having almost never been able to get on the ea severs when I want and resulting in several router resets etc etc to rarely get any sucsess.
However, after looking into it I have found my router is a little to clever for its own good sometimes and causes issues with certain games. By forwarding the ports that ea severs use I have eliminated this issue entirely. Ever single time I play the game it connects at the start as you would expect.
The ports that I forwarded for fifa 11 are:
31400 - 31499 (TCP)
There are a few others, but they are not really needed I have found as these will get you connected and allow you to play as you need to.
It is also a good idea to forward all ports that the xbox live service likes to use.