I encountered this bug also, it happens when you swtich weapon when firing from a shotgun or something like that, i know it happens right when i shoot i always end up pressing the switch weapon button by accident, and everytime it freezes for me.
I tried it on 2 of my xboxs one is chipped, i have no clue what the chip is, and i also tried it on my softmodded xbox, both of them have the bug, and yeah about the multiplayer request, that would kick ass and maybe if you could put your own face in the game lol, well im sure thats like the simplest thing to do but yeah lets start by fixing bugs. <