Just thought i would post a thread on How to play Dead Ops on Blacks Ops in prone.
If you haven't already done so, Break out of the chair at the main menu by R2 and L2 and then make your way around to the terminal. Once you are on the terminal type in 'OA' and then this will load up the Dead Ops Arcade.
Once it has loaded and just before you see your players hold down the buttons 'Square and Circle' at the same time and this will make your character lay down.
This glitch works for XBOX as well as PS3 and also this works online.