First of all, Melody, it could be a mesh problem. Also, check your particles folder to see if there is any 1_0 for example, bonfire_1_0.particle or something like that. Delete the duplicates, basically.
If it is still not working, I'd suggest checking to see if the heightmap is greyscale, for example, it could've glitched or changed somewhat, not that I know though.
Also, it could be a problem with the exporting. Check the files, and see if there is anything wrong.
That's all I can think of. It could be a problem with any small thing in the map truly, maybe even the coding of the files of the map.
Might want to post your problem in Game Help, perhaps? Uninstalling and reinstalling is on the bottom of the list in my opinion, but try it perhaps, if nothing is working.