Do you have a 360? If so, go to the System blade, then Memory, then highlight the Hard Drive and press Y X X LB RB X X, and it'll ask to do maintenance on it, say yes and it will delete your 360's cache, meaning you'll have to re-download updates (not downloads you pay for, just game updates); then just keep trying and doing the same thing. Or, you could aslo delete the map data and just keep trying again. That's what I did, and it worked eventually.