I don't know if anybody else is having a similar problem, but the trainer/editor file doesn't want to work for me. I am running Windows 8, I launch the executable (fc30, I think it's called).
I click okay in the dialog box, and the OS then asks me which program I would like to use to open ".tmp" files.
It's pretty strange. The trainer (fc3.exe) works just fine for me, with no compatibility issues. Tried another editor, the one for Borderlands 2. That one works just fine. Very strange.
Anybody have any idea what's going on?
Try to run the game as Admin. If you only use the trainer only version, there is no such problem.