The only time this has happened to me yet is when in the public match create-a-class. The error I get is "Hunk_UserAlloc: out of memory. Requested 8448"
I bought the game on demand so it's located entirely on my Xbox 360 hard drive. The crash actually happened while I was out of matchmaking, customizing classes in the multiplayer menu. I lost all the changes I made to my classes since the last time I entered matchmaking.
Any word on this? I can't find any reference to it online except for years ago, and there was no solution for it.