Sound, but no picture on HD channels

[KNL78]

So, I have sound, but no picture on HD channels... The nonHD channels have picture. Any tips?

[CCAndrew]

Are you paying for HD? Usually that’s what happens when you don’t

[KNL78]

Hmm, I don't know! If that was the issue, the sound would still come through on those channels?

[CCAndrew]

Do you have an HD box? Have they ever worked?

[andyross]

Exactly which model box do you have? This almost sounds like your area finally upgraded to MPEG4 video, and your box doesn't support it. I thought Comcast had upgraded everybody by now.