i have this exact same problem with my onkyo sr-803. after spending over an hour on the phone with onkyo, cox cable (my HD-DVR provider), and scientific atlanta (DVR manufactuer), i found out the problem with both your denon and my onkyo is they both use HDMI version 1.1 and I would bet the rent your cable box is using HDMI version 1.0 the same as mine. I was also told by my cable provider that they have "no imediate plans" to do any firmware updates re: HDMI. for this very reason I,m going to return my onkyo and get the Outlawaudio 1070 (uses DVI switching and was told by them that it will work for video only even with the different HDMI versions, I'll just have to use optical for audio as I'm doing now). HDMI ver. 1.1 is not compatable with ver. 1.0 and has a "handshake" problem (defferent HDCP language)