I had this problem with Edwina. She would occasionally poop in the dining room and pee in the powder room sink of the house we owned when she joined us. Interesting to note, we moved and even though there was entirely new furniture and carpeting in the new dining room that was the ONE place outside her litter box where she would "have accidents" in the new house. Fortunately she found the sink in the powder room in the new house to be uncomfortable. In fact, she once started to pee in the powder room sink in the old house in front of propsective buyers. Fortunately our realtor was an animal lover, good friend and quick thinker!

As to the solution. I consulted my sister-in-law, who is a vet. She advised putting Edwina in her box about 1/2 hour after she eats her evening meal. Stand there with her and praise her, talking lovingly the whole time. It worked. We felt rather stupid but to this day she enjoys us "cooing" to her while she does her business and she hasn't had an accident since (year and a half.) I suppose it isn't that different from toilet training a child? When we have canine visitors or other disruption to the routine and she gets a certain look we know we need to help her. We just set her in her box and coo away!