There is no picture on my hd nbc channel. the dvr is recording but there is nothing on it. The nbc sd channel is broadcasting fine but not hd. it appears this has happened to others when lineups are changed or people in between markets. What gives?! I want my nbc!
It may be that they are finally changing over from MPEG 2 to MPEG 4 im your area. The local 1080i channels are being left in MPEG 2 and all the other HD channels are being converted to 720p in MPEG 4.
Some older cable-boxes cannot handle switching between MPEG 2 and MPEG 4. You should check with Comcast to see if your cable-box and remote need to be exchanged (No Charge) for a newer compatible cable-box.
The MPEG4 conversion should not affect broadcast channels, as they are passed through as-is. Broadcast is still only MPEG2 until the new ATSC standard is approved and devices that support are available for awhile.