*waves*
Try the things said above, and refer to the tutorial if need be, but also make sure that y’er map file name doesn’t have any spaces. If it does, the file won’t load and may be causing the game to crash.
Also, it may be that ye ‘aven’t compressed the image properly. I don’t know how Photoshop works, but to simply put it, select all and copy visible then paste it on a new canvas and save as a .jpg. There’s something on FH that makes the game crash when layers and whatnot are involved with height maps. I’ve yet to figure out why, but that’s just how ‘tis.
Hope this helped ye, deary! Best of luck map making.