My bet is the compression protocol Comcast is using to cramp more HD channels over the same coax. DirecTV is going to MPEG4 to expand their HD lineup. Not sure whether using the newer DirecTV's H21 HD receiver or HR21 DVR have the same viewing issues. Like I had indicated earlier, I have the same TivoHD unit going through HDMI to another similar size LCD TV but without the receiver in between; and unfortunately I am seeing the same pixelation issues. Another proof is I still have a Comcast HD receiver connected to a HD 34" CRT TV and I saw major pixelation on fast motion HD movies.