Thanks for the replies.. I've been busy all weekend but I wanted to respond to a few questions here.

I would LOVE a feline behaviourist but I just don't have the money. I can't afford to take her to a kitty head doctor.. because it's a specialist I'm pretty sure a visit alone would cost lots of $$$ and that wouldn't guarantee any results.

The couch is not a place the cats normally sleep. They have lots of trees/chairs/window seats that they use, and I hardly ever see her on the couch. The only time I saw her there was after I got home from a trip, and the pee was already there (I hadn't discovered it, but there was a smell in the room that I couldn't pinpoint).

Bassett has ALWAYS peed outside the litter box, always seemingly random (ie I never really know why) and there are certain places that are a sure place for a pee mess. Any time there is a pile of clothes/blankets/pillow/etc on the floor, she will pee on it. Any kind of box, either empty or not, on the floor and even sometimes on the counter, she will pee on/in it. I can't have any box anywhere in my house, unless it is closed and up off the floor.

Today though, I saw something that might be part of it. Bassett went into the litter box, was doing her thing, and Nutmeg shows up from the other toom and just started attacking her IN the litter box! I don't know what that is about, but I might have to start medicating Tilly and Nutmeg too, because they are both agressors in this situation. Sigh. I live with a buncha mental freaks