Are you 100% certain that the gamertag you're using is the one that owned the game on the 360? Does it say you own it on xbox.com?
I've only ever owned one. But going on Xbox.com has it at $9.99 still...but I played it this morning on my 360.
Huh...going onto xbox.com if I put in Mass Effect and Super Meat Boy (the two I have working), it says "THANKS FOR BUYING" when I click purchase. But Perfect Dark still has the price and I can buy it.
What could be causing this? I wonder if it's because my account used to be Canadian and now it's American and the license switch screwed up something...hmm..