'mini-blinds' on NBC in orange county, ca -adelphia

For a few days now, NBC has had lines across the screen that look like miniblinds -- they move, but not completely from top to bottom like I would think interlacing lines would look. The lines aren't there when I watch OTA broadcast through my HD receiver. Is this just a cable problem?

I have adelphia in orange county CA...anyone else having this problem?

I think NBC (Ch. 4) is the only channel having this problem.

Nate