Have you been using the unlimited health option?
(See link below)

www.cheathappens.com/show_board2.asp?headID=65664&titleID=10899

You need a weapon modded for high damage and capable of gibbing. For the Hunters, this means a high mod sniper rifle, fully configured for damage and criticals.

The trainer won't help with gibbing.

I just figured, the more people that mention it, the greater the chance of a fix