I've downloaded the new trainer and tried everything Welce did; ran around a bit, chopped down a tree, got hit by a slime and killed it, before attempting to activate the trainer. It still gives me the same 'cannot find game code' error. I am currently running Windows XP SP3, and running the game in windowed mode, instead of fullscreen.
I'm getting the same issue, win7 64bit ult. Noticed the trainer doesn't know what version of trainer it is, also after i hit F1 in-game and wait awhile about 60 seconds or more a small window comes up saying code not found, i say ok and then the trainer says activated again, so i press the hot-keys and it says activated but it doesn't actually take effect. I hope this will help pin point the problem.