Bad Company 2 Vietnam DLC Serial

I can play Bad Company 2 from Steam but I couldn't activate my Vietnam DLC serial key in-game. I then managed to activate the serial key through Origin. Now Origin shows that I own the Vietnam DLC but I can only launch the main game through Steam because I purchased the game from Steam.. When I try to access the Vietnam DLC in-game, I manage to sign into my Origin account but when it asks for the serial key for the DLC it says that it's already in use! Well yeah, it's in use in MY ACCOUNT, the SAME account that I signed in with in-game. So this is a bug that needs fixing!!!