After disabling Steam and running Crysis 2 by itself w/o the overlay, the third round of Team Instant Action featured a player using an Aimbot and a Speed hack. He was sprinting through the map, headshot, headshot, and headshot. This is the same hack I saw yesterday when I could still use Steam overlay in game.
I really love Crysis 2. Has anybody else seen this issue too?
(Edit) I should mention that I know Crysis 2 isn't using punkbuster. Besides, I can use the Steam Overlay for Bad Company 2 which I also bought from retail, which does use punkbuster.