Originally Posted by EASpenser
There is also a forum post here that can help with some of these issues: http://forum.ea.com/eaforum/posts/list/365758.page
The most common are that you do not have the correct persona selected (discussed previously in this thread) and that your gamertag is already taken (it was probably registered with a previous EA game, like dragon age for example, and you are logging in with a different email/password). If this is the case you can recover that account info with the password recovery.
Thanks man This Achievement has been a pain for everyone