Me and a friend both tried signing in to play GOW2 with another friends' profile. We found that both of our profiles would crash everytime it goes into the game. We had tried removing and recovering the gamer tag, clearing the cache and updating any updates needed, turning off networks/modems etc and testing the xbox live connection. Nothing seemed to work. It didn't even say that our profiles were corrupt. We were stuck with what to do. This had happened to a profile I had before. Anyhoo, we asked around and found out that you go onto GOW menu and choose the training grounds option and choose Lesson: 5 which should be submission. On this, you log into your profile whilst it is loading this up and from then on you can use your profile however there is a downside - you will be ranked back to a 1 and have to start it all over again. Hope this helps as we spent hours trying to find this out.