One of the major updates a year or so ago changed how to recover your gamertag which made the process a whole lot faster. I think it was around the time cloud storage was added.
To add to this, the guy that emailed me about this particular problem said that to wasn't necessarily a fix per se for this game but something they noticed had worked on some of their other games. It's a good thing to try in the future for any other problems you it run into with any other games.
Also, just to add a touch of class. The guy that I emailed at Most Wanted Entertainment is apparently the studio director. After speaking with him I beat the game and in the credits it had his name as studio director. I thought it was kind of nice that someone that high up in the company was helping out with fixing this problem.
Well I get up in the morning and I get my brief. I go out and stare at the world in complete disbelief. It's not righteous indignation that makes me complain. It's the fact that I always have to explain. - Van Morrison