Sounds like you hit the channel up button a few times to unstick it?
Take it back if you can.
We could give you all kinds of advice about opening it up and troubleshooting but once you start down that path you reduce your chances of warranty coverage.
Reminds me of a tech malfunction from a few years ago. My VCR would stop in the midde of the tape. The auto-stop tension sensor was faulty, but the deck was under warranty so I took it to Sony's regional service center. The tech had the sack to suggest I close my blinds to fix the problem. Seriously, he explained that neighbors often point remotes through the window.
