This is not a difficult scenario to reproduce "in-house." Here are the steps to follow:
1) Turn on Xbox
2) Get hit by Clan nX party invites
3) Join said party
4) Turn on Crysis
5) System fails on "initializing" --hard freezes
6) Try again
7) System fails on "initializing" --hard freezes again
8) Try again
9) System fails on "initializing" --hard freezes again
10) Get out of party
11) Boot up Crysis and Multiplayer
12) Join on Squad and join party (chance of hard-freeze reduced to about 20 %)
13) Stay out of party throughout the night (chance of hard-freeze reduced to 5%)
*******CryTEK please acknowledge this PROBLEM! And either state a fix is being worked on, or this issue cannot be fixed due to RAM limitations or w/e reason you come with. We just need to know that such an obvious problem isn't going unnoticed.