I'd also like to add, the Blu Ray player doesn't have this issue. It sends the audio out the digital audio, as it is told.
This is what befuddles me in that if the TV monitor was the culprit here it would have affected the Blu-Ray player settings as well, but it doesn't even though the hook-up is identical to the cable box! Certainly the component input will be fine and it certainly not a big deal one way or the other but it is interesting what is happening here. Did you attempt any of the detailed cable box menu settings I suggested in my previous post because I STILL don't believe the TV is the issue. Something in the cable box is not locking in the digital audio properly.
Like I said previously, these models should be able to send out the coax audio and HDMI video simultaneously without issue.
