Briefly, the bug seems to be affecting 360 copies of Rock Band 2 where the primary band member has a Live enabled account and another band member is rockin' out without any Live membership. Then, for no reason and usually further into the game, the bug glitches and deletes your entire band and all of its progress. Major, major bummer. Harmonix hasn't acknowledged or addressed the problem yet, so we have no clue when or if a patch will be released. For the time being, we recommend playing Band World Tour with all Live enabled or all non Live enabled accounts. Please, rock out carefully.