Bugs related to key generators (why is that?).

It is unlikely that this happened for no reason. Most likely, some of the text files describing the game parameters and the keymaster's tent have been damaged or replaced. Did you install anything on "Heroes" beforehand: a patch, a mod, or any additional files in the DATA folder? Was there a computer crash? Browse the "Heroes" folder and the DATA folder, look for new/modified files. Once you identify the cause, you can decide what to do next. The simplest solution: reinstall the game.