Anyone else having this problem? I can watch regular NBC (ch 4) and I can watch HD channels (e.g., Fox, 505), but NBC HD 504 isn't working at all. It just bounces you back to the channel we were previously watching.
Last time I had a problem similar to this, it was a bad box that couldn't properly tune the correct frequency any more. Give Fios a call and have them run a check for you.