When I try to install my DLC from Fallout 3 GOTY from Best buy, Games for Windows Live claims I have an Invalid authentication key. I don't need Games for windows live for the main game, so the game runs fine if I don't install the DLC. But as soon as I try to install it, it always tells me the key in invalid, and I have to uninstall everything 'cause Games for Windows Live locks up the games ability to load saves.

Does anyone know how I could fix this and use the DLC?

I have windows 7 on my computer, which runs the game just fine on High-Ultra.