I also have problem when pressing F1 at the main menu and the game crashes, but i found workaround. Run the game and immediately when you get the Crysis 3 splash screen, press F1! If you wait longet than that the game will crash. For me, works like a charm!
any guys having trouble with the trainer use the no cd version v1.1 reloaded version on gamecopyworld pwizard has already said this, so guys read things properly
That is the no-cd version I found yesterday. So far, it is working better with the trainer than the original .exe, i.e. less prone to game crashing or locking up.
For others, be sure to save a copy of your original game .exe, which will likely be needed when you play multiplayer online or when Crytek/Origin issues another patch update.
Crytek developers are already preparing another patch to fix or adjust certain game elements and included in their list is a more thorough anti-cheat. This may or may not affect the trainer when using a no-cd .exe in single player.