The thing does save. And save correctly. It's just message box receives wrong code and complains. It happens only when you overwrite the game. I promise to release hot fix to this tomorrow ASAP.
From the other thread. I really hope this fixes the problem I'm getting (not really sure what you meant by message box) as I've never manually overwritten a game, although I'm assuming Quick and Auto saves count as overwrites.
I still lose the map (goes black) when I manually make a new save, though.