Browsed through a bit of the thread and didn't find this mentioned anywhere:
For, apparently, some very specific reason, if I level one of my mages from 5 to 6 after hitting the F12 button once after the it loads (Since it apparently fixes the stats, or is it the other way around? Well, alters them, if nothing else.) I get the attached error, and the game closes. If I don't press it and level to 6, however, then it's fine, and on every other character (including other mages), I've seen no similar problems. (This isn't really a problem for me in particular, since I've already found a workaround for it, so it's just more curious than anything.)
So, while not gamebreaking in any way, I figure, it may be vaguely helpful to mention it, and if it already has been, well, I had good intentions.
(I'm also assuming it's a very simple error, if I had anything more than a conceptual knowledge of programming, this message would be even shorter.)
(Oh, and of course, amazing game. Always great to see a well designed RPG! Unlike the thousands of "modern", broken, action RPGs we see today.)