The HDD Upgrade wizard in the Xenium OS is a great tool. However, in copying over all your gamesaves, soundtracks, and other data from your old hard drive, it also copies over the files in the E:\CACHE folder. These cache files are linked to the original HDD, and will cause Live enabled xbox games to lock up.
The solution? Delete those files! Just delete the contents of the E:\CACHE folder (leave the folder), and they'll be properly recreated upon reboot. Your games will all work now! That's it!
(This is an old issue, but it's still a relevant one and thus I'll leave this pinned)