I wish I could help, I have a similar issue, well, almost!!
I go to the Fox Digital Copy site, enter in the activation code, choose iTunes format, and get a message 'Please check back in 48 hours for iTunes redemption'. The message has been the same for the last 42 hours.
I tried entering the same activation code directly into iTunes, but then I see the same message that you mentioned.
Did the Fox Digital Copy web site tell you the code had been redeemed ok?
Paramount havve a great system for disk-less digital copies, wish Fox was as good.. or at least worked!
I know this was asked a while ago but I had the same problem and was in search of answers. After realizing no one figured this one out, I stumbled on the answer by accident. With iTunes 11 if you have the digital copy disc inserted you should be able to use the Library menu (the drop-down on the top left where you can switch between music, movies, etc.) and the disc should appear as a selection. Once selected it should automatically take you to a special redeem page for the disc. Input the code and you should be golden.