Sorry, I've been out of town, so I didn't see your post until just now.
Please click here
to read about inappropriate pooping.
Whenever you have elimination problems, the first thing to do is to take the cat the the vet. These problems are most often due to medical problems.
This happens in my house occasionally when my little bully cat won't let the shy cat get to the litter box. If you have multiple cats, this might be the problem. Having boxes on each floor of the house can help with this.