That is weird. I bought Crysis 2 a week ago and downloaded the latest trainer and it runs fine for me. I don't believe it has any anti-cheat functions.
This is the first time I've ever had one of Cheat Happens trainers not work; they've been totally reliable, so this is weird. Bought my copy at Hastings - Limited Edition, retail ver. 1.0.5xxx. Run cheat as admin, put trainer's exe file in same directory with the game's exe file, tried upgrading to 1.1 and 1.9 vers., and simply cannot get the trainer to engage at F1. The only thing I haven't done is logon to EA's multiplayer site - I don't do multiplayer.