Code has already been claimed

I received a beta key from the contest recently, and just entered it into battle.net. When I do this, an error pops up saying that the code has already been redeemed, yet this is the first time I have tried this. I copy-pasted the code exactly from the message popup, so I know I didn't put it in incorrectly. Maybe it got stolen somehow? Any advice?

Edit: I have also submitted a support ticket to Blizzard, and am waiting for a response.