Some people are reporting an error that the codes have already been disabled.
The code has been disabled. Please review the code and try again. If you have further problems please contact the Customer Support team.
This may be a temporary problem since it has happened in the past. It may be related to people being confused and putting in the Battlefield Heroes code on the NFS World site instead of going to that game's website.
Keep trying until the January 17th cut-off and good luck!
Ok, official response on this issue.....