We feel your pain. Go to

http://www.catsinternational.org/art...ing/index.html

and review their wonderful Unabridged Guide to Litterbox Problems.

One of my fosters was an exceptionally finicky cat. She got two litterboxes.

You might also try posting in Cat Health--this forum is not visited as much by other members who have experience in this area.

Good luck to you and Ringo.