Hmm..
Have you tried re-installing?
If not, rename your current FH folder to something different like.. "FeralHeart_" or somethin', and attempt to re-install. o: Copy all the files from the original folder related to the map and put them in the new folder and attempt to export?
If this doesn't work, it might just be the map itself. If it's super big and/or filled with a bunch of meshes that would otherwise cause the game to lag, it might just be that FH can't handle exporting the map and therefore crashes.
Or, if you'd want to try, try removing all particles from the map and exporting, I know that they can be really tricky sometimes.
Just trying to throw out some ideas!