Lots of people on the Rock Band forums are complaining of a pretty heinous multiplayer glitch in Rock Band 2, which seems to only affect the 360 version. In a nutshell, it strikes bands with Live Enabled gamers as the primary account, and non-Live enabled as the secondary. The glitch wipes out your band in tour mode, and forces you to start over. Particularly aggravating is that it seems to wait until you’re a ways into the game.
Rock Band 2 Glitch Wipes Out Bands?