grr i have the same problem!!! a few months ago it was fine no problems everything played good. then i got a new hd(upgrading the xboxes 80gig to a 160gig) used my pc to transfer all of the games across, and now about a quarter of them either don't start, freeze at the loading screen, or freeze when you press a button in the main menu. i have tried about 10 diff. bioses, m7, m8, m8plus, 5 or so versions of x2, ind bios, and all have the same problem. unleashx, avalaunch same problem. even some dvd games have stopped working.
so from that i'm guessing that maybe it does have something to do with the hdd, even though mine were similar(both seagate 8mb cache 7200rpm barracuda drivers, only diff was the size).