Cat poop problem?

I've read the posts concerning behavioral problems and cats pooping in places other than the litter box. I've tried everything but I have a cat (1 of 3) that is pooping in my basement, even though each cat has his/her own litterbox that is kept meticulously clean. I've even put another box right in the spot the cat has started pooping in to no avail.

I've heard that putting moth balls soaked in vinegar in the spot where the cat has been doing his business helps keep the cat away from that spot? I haven't tried this yet, but I'm running out of options.

Any advice would be most appreciated.

My persian tom developed the same problem when we lived in a house with a cellar - for some reason he associated it with the garden, I never did work out why. Nothing I did stopped him, in the end I just had to stop letting him into the cellar.

Ranger

My family has an "Atrium" which is basically a big hole in our living room that is filled with plants, its pretty cool. Except our first cat Blue Eyes used to Poop in it cause he was an outdoor kitty. We solved this by dusting it with the carpet odor removers (fresh step? no... that's litter... grrr) regularly after we watered, he hated that stuff. I don't know if it would work for you, but it is a though. Might smell better than mothballs.