I got this problem /all/ the time whenever I tried to export detailed maps, but normally I managed to get the map out before FH crashed permanently and I was forced to re-install. Recently though, I've found that if you go back into your my_objects folder and check to make sure there are no particle files or other odd files that are messing up your map's export process, it can help fix FH. It's not easy and time consuming, but if you go through your files carefully and check to make sure everything is where it should be, you might come upon the file that broke your game. Otherwise just take /everything/ out of you my_object folder, and take out all of your custom map files as well. This should help get your game running again so you can begin testing what went wrong. Please note that although it did fix my game, it might not for you, but I do hope that this might help out!