This happens all the time when I leave my NBA 2k6 disc in the console after shutting it off. When I go back and turn the console back on I get the same error message about 4/10 times. My solution is when Im done playing each game, exit to the 360 Dash and remove the game.
Before playing any game, I always let the 360 boot to the dash 1st, then I put the game disc in and let it go from there.
Hope that helps