When I got on Minecraft today day I bought a new mash up pack in the market place and every time I get on the game and try to use and or any other downloads such as Worlds and texture packs it will sometimes say "Updating 10000000 out of 1 packs" ( I used 10000000 as a representation of the large numbers it normally shows) So what I do to solve the problem is restart the Xbox because if I just restart the game it doesn't work still