Thank you for the details, which I've printed for safekeeping.
My iTunes Library is all there....my Songs, Downloaded, Artists, Recently Added, except underneath those categories "All Playlists" has nothing in it except "Genius". Also "hide" is next to this.
I bought some songs last week, added them to 2 different Playlists. Last weekend I selected songs from my Play Lists and listened to them with no issues. I have not updated anything.
Sometimes after iTunes automatically updates, I find that my Playlists disappear.
I tried to find where they are saved but get terribly lost.