I've been trying to install the content required to play the single player compaign on both of my xbox 360's and both have failed. I get to about 45% before it stops and says it can't find my hard drive anymore. I can't play the single player at all without first installing the content. Is anyone else having this problem or could it be a disc issuse? I'm able to play online with no problems, but i want to start working on the achievements.