I checked, and I'm running the exact version that this trainer was written for...wait: Let me see if the 32-bit version works...yep, that's the problem: This trainer wasn't written for the 64-bit version of Crysis Warhead. For folks trying it, the trainer doesn't "see" the 64-bit version.
That may be why some people report that the trainer doesn't work; they're running the wrong game EXE.
NO! I don't know what the problem is, but NOW the trainer can't "see" the 32-bit version of the game, either. Five minutes ago it could. Trainer's broken.