Hm, I'm not a mapwiz as such, but I found a few things that may help:
I suggest you try clearing some things off my computer.
If you can't delete unwanted/unneeded files.
Lastly, try reinstalling FerelHeart and backup all files from the game that were changed such as loading pictures, cursor, etc.
Head into your FH > Media > Particles/Objects and make sure you don't have any files with _1 etc added to them.
Duplicate particles and others can cause the game to crash.
Ah, yes. The particles could be the culprit. Go into your C: >>> Feralheart >> media > particles and delete any ending in _0, _1, and so on. Sometimes particles double when they are exorted, causing the map to crash. Particles can also get themselves into the my_objects folder, so it wouldn't hurt to check there. ^^
Also, make sure your map is 513 x 513! That's very important.
If you don't find particles in those folders, search them in your PC.
Lastly, does your map have many objects? That can cause the map to crash.
If this doesn't help at all, I hope you find solution. c: