Dave,
I have the exact same boat and HAD the exact same problem. I did fix it and from my experience, you will have to always do a bit of "maintenance" to keep the posts from going in and out smoothly.
I think TOXIC is right about the lubrication swelling the seat. I tried lithium grease and WD40 without success.
At one point, I could only get the bicycle seat post out of the seat by twisting. The seat twisted in the socket then the button would not pop out to lock the post in the seat. I tried and tried to turn it without success. I then carved the locking hole a bit bigger just to get the post to lock. I ended up calling Swivel-Eaze/Zebco and got a new sleeve.
I did sand the post (lightly) and the seat and got marginal returns. And yes, the carpet fibers will cause a problem. It was the carpet fibers that led me to the solution. Keep the post and the seat completely dry and clean. Just use a dry or slightly damp (with water) rag and wipe the post and seat out. The posts should slide in and out very easily.
Once you get the post(s) out, keep everything clean through the season and in the spring and I think your problem will be solved.
Bon chance....
Mike