Hello, FlamingRedRose, in order to figure out why your game is crashing, I am going to recommend you find Feralheart's directory (located in C:\Feralheart) and opening FH.log using notepad or another text editor. Copy and paste its contents directly here after you start the game up and it crashes.
Similarly, I would also recommend you try Vilivikhorith's custom log file available at the following link.
https://feral-heart.com/smf/index.php?topic=61007.msg841371#msg841371 I use the file myself and I feel it is a very useful tool for viewing the game's logs, better so than the original FH.log file that is included with the game. If you decide to try it out, copy and paste all of its contents here after the game crashes.
Either log file (the linked version more so) will hopefully lead us in some direction to why your game is crashing. Considering it crashes before the game fully reaches the main screen, I doubt it has anything to do with a heightmap or mask issue.
I remember that before this major update (neq maps, etc.) creating maps was easier and no such big problems (like right now) didn't happen..
I actually have heard many similar statements and whether they not are accurate is up for debate. Still, I feel they are valid and there may be an issue stemming from an added file. If you are up for it, you could send me your map's raw files—including the objects, heightmap and mask, etc. that are associated with it—so I can test it out on an older version of the game. In your map, do you use custom objects?