I hate partics ther the worst xD >.<
(try renaming the .mat folder if it fails)
OK what i do is, single partics i put all in the Particle folder, and to use them go into feral heart>>tools>>objects maker>>effect maker>>Particle
then type in the name xD make sure to export it btw, and if it doesnt show up, get a small object make it small and do the same thing, and rename it and export!
and so your game doesnt crash go back into the Particle folder and delete the doubles
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if that doesn't work then do as the post above says, _ try the my_objects folder, i'd help with that but i dont know how that way works unless its in a object file or what ever.
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if all else fails, do as the first suggestion was but move materials into the material folder, my_object folder and textures folder.