I think this is common, however new to us. We have had our cat about 4 years now. Suddenly he is pooping on a rug in the living room. Peeing in the litter box as usual. Nothing has changed, no new litter, no few food etc. Any idea?
We have had a series of posts within the last few days on this very behavior problem. Skim through some of the other posts and see the many great suggestions.
I wrote a post a few days ago about my cat also doing the same thing. I got some good responses, so maybe take a look at the thread. Its titled "Regressing".
Good luck, I can sympathize, its so frustrating!
It is not really all too common. Usually it indicates that something has happened to upset them or they are not happy with the litter box. However, it can also point to constipation. You may want to have a vet take a look.