Query on my 27" Color Magnavox TV

Hi, Everyone -

First-time poster here, so be gentle...

I'm wondering whether anyone has experienced the following:
- a few nites ago, my relatively new 27" Magnavox color TV started experiencing a horizontal black area starting to move down the screen - like a shade being pulled down on the screen. Right now, it's reached about 2-3 inches, and appears to have stopped moving down --- for now...

Anyone experienced this?

Thanks.

Golf