So, when I save a particular map that I have, the map editor generates about 28,000 Master_Quest and Burning_Lands tiles in the map file. I can see this in the XML, when I read it. This causes the game to hang. when I delete these entries, reload the map, and resave, it puts them back in.
Tis a strange bug.
I believe from reading the other map.xml files with the game, this sort of outcome is unexpected.