How fix?

Your client ain't sober yet. It got a hangover.

Must've been the good stuff then. I had to unzip a new copy of the game over the old copy to get it working. Something went wonky somewhere.

That data is stored in your moa file.

I would hazard a guess that the moa file that it is trying to read is corrupt or not a valid moa file.
Try reloading your saved file again and see if that fixes it.