ok so i am still having the same damn problem I was never able to play the demo and now i cant play the game i paid for the game keeps telling me that my login information is incorrect but i can log in just fine at gamesas.com WTF
You can skip the multi player login and just play single player.
I however purchased a game that also contains a multi player component that I would love to play, EA and GameSpy seem to enjoy stopping me from doing this though.
I had this problem with the demo, I know the frustration it cause. My work around was to make a completely new email with gmail then use that gmail account to make a new account on the gamesas tab ingame.