Quote Originally Posted by Niwashi View Post
By any chance, was one of the two bought through Steam and the other not? That could account for a code working on one and not the other, since Steam and non-Steam codes can't be mixed on the same account.

If the game was purchased from Steam, then all expansions have to be purchased through Steam, and if the game was not purchased through Steam, then expansions cannot be purchased from Steam. (It seems like a pretty dumb rule to me.)
Well, back in v1.0 you could only buy the game from the store on dvd boxes, so those who played back than need to register normal windows keys. If the game was bought on steam, you have to use steam keys. ARR was added on steam on its launch.