XBox 360 HD DVD Can't Play This Content: C66700B

Trying to play the very first HD DVD that I've rented ("The Host"), I received an XBox blade popup that said "Can't play this content. Reason code: C66700B." Does anyone know what this is? Please don't tell me there are incompatible HD DVD formats or DRM restrictions that say "Oh, hey, sorry, we don't approve of your TV."