i guess this is what i get for pestering my friend up at gamestop for a copy before the release date lol! (bah i had to trade a 12 pack too )
anyhow i have a similar issue to the fellas above me. Reg trainer activates, yet i do not hear an audio response for the num keys at all. i hit them then hit esc to go to the pause screen (i guess thats what its called) and i still hear nothing. im going to see if its just win 7 64 giving me trouble and remap a few primary keys (ammo and health).
If you get it to work please post back what you did.
Not sure why it isn't working.. I have a few other cheat happen trainers for older games that work fine.