This often happened to me, but then i changed account and it stopped, it can also depend on your internet, my friend had similar problems too, but after uppgrading his internet it stopped...

That's been happening to me too, except with Broken Steel. I don't know what to do about it though, I've tried different XBox's different profiles. I think there may be like a small programming error somewhere on the disc itself that makes some parts of the DLC incompatible. (just a theory, probably very wrong)