Alrighty, let's see...
First off, have you exported any maps recently?
If so, go into your Feralheart folder, then go into Media, then your Particles folder, and remove any files that end with _0 or _1.
If not, there's probably some glitch in the game. The easiest thing to do would be to uninstall, then reinstall the game. This should reset any goofy files, and allow the game to run properly.
I hope this works for ya, floof. c: