I just bought and downloaded the game, and after an hour of gameplay an error came up saying "This disc is unreadable". I don't even know what's wrong. The same thing had happened to my Assassin's Creed 3 - which is on a disc, yet there were no sings of problem and I was just replaying the story. Could my XBOX have a problem with Ubisoft, even though I downloaded and played Assassin's Creed 4 just fine? I already tried deleting the game by itself, and then I tried deleted the saved content by itself.