HDTV Pixelation on some channels. If you have checked connectors, used digital splitters, converted from copper RG6 cables to aluminum RG6 cable, got an amplifier...and you still have problems. DO THIS: Press the Xfinity button on your remote (like going to on Demand), arrow over to gear icon on the far right past Apps, select (hit middle button). Arrow down to "Device Settings", click middle button again to select, arrow down to "Video Display", hit middle button to select, and MAKE SURE your video output Resolution is at least 1080p. If you are using a Hi Def box, 720p or lower will cause issues. Arrow to 1080p and select. Then, if you can, either restart the main box online, or unplug and plug back all boxes to reset the signal. You will be restting the system to the appropriate frequencies for HDTV. You're welcome America !