I had a similar problem. Same lockup during loading screen - it just goes black and the Xbox stops responding completely. After the Jan update, instead of a total unresponsive Xbox black screen, I get a message that the hard drive is no longer attached to the Xbox.
Lionhead and Microsoft showed their f!@#$% asses on this game. There are so many crashing issues. I have no invested interest to start a new game - because this is just going to happen again. When I emailed Lionhead about the issue they just referred me to their update page and said that something is being done about a fix to some of the problems out there.
I guess ours was not addressed.
Wolf-