Comic_Sans does sound like a font. In fact, I could be wrong on this, but I think its the font someone mentioned once that the game uses, so it would make sense if there was a problem opening the game if it wasn't there.
Here is the question though: Why is the font missing? Is it inculded with the game or does the game look for the font on your computer?
I would try the Northern Kingdoms mod and see if you have the same problem trying to run the game with that mod. The Mod uses a different font than the regular game, so it might run even without the Comic_Sans font...
EDIT: By the way, I noticed you are the same person who had a problem getting the editor open. Is it possible you changed something that might have effected the game when you were messing with the editor problem?