I have a similar problem with the SA8300HD DVR from Comcast and my Sony XBR2.

For 6 months the HDMI connection was great. Then soon after one of the Comcast software updates, I started getting a "red" screen every morning and would have to reset the cable box every morning (coincidence?) . Once or twice I got a message about HDCP not being established (or something similar).
After several weeks of trying different settings, different HDMI cables, etc.,I started using the component cables & have been happy since.

I will occasionally try the HDMI connection to see what happens, with the same bad results.

The TV had no problem connecting to a Toshiba HDA3 and a Sony PS3 with HDMI cables.

Try component cables with the cable box. I wasn't able to tell the difference.


Oy