online code

hi,
i bought fifa 2011 a couple of months ago and there was never a problem when i played online.
but recently, my game (ps3) started asking my online code to play fifa 2011 online.
when i enter the code, it gives an error, and the code hasn't been used before by someone. some friends of mine have the same problem so, i want to know what the problem might be?
can somebody help me with this problem :)?