Ok this is not me asking for help i am just stating a fact...
I ran into this problem with Tony Hawk's Underground nothing they tell you helps at all and there is no point in buying a new Xbox 360 all you have to do is go to the Memory find the game (older saves you have on it) and delete everything from there.
Odds are you are going to be starting over anyways so this is just letting you all know so you are not wasting your money on another Xbox 360.