did you place the ndless_recources in My Documents\ndless directory? since when you place it just in my documents it won't work.. and you first have to place it there, and then install ndless, not the other way.
Also if you're trying to open pure wad.tns (ndoom) or gbc4nspire files, they won't open (i don't know if this was the case, but it might be possible)