it happens like that if you add a folder that has one of those .m3u playlists in it. it takes every song in there from the .m3u and then also adds the individual .mp3's themselves, so you get 2 of every song. easiest thing to do is just delete the .m3u out of the folder before you add the folder with itunes. at least this has been my experience. if the folders that are causing the problems dont have a playlist file in it then i dont know what is up with it.