Clients cable went out, cable company came out to fix it and found a bad HDMI port on the Denon receiver. To get it working they used a different port on the receiver. They also replaced the old cable box with a new Contour box.

I came out to program the remote and noticed the system now has a 60 Hz hum coming through the speakers in zone 2 when listening to cable. Zone 2 is RCA out of the Denon into a Parasound Zone Amp When I disconnect the RG6 cable from the cable box the 60 Hz hum goes away. I doubt its a ground loop since the system has been fine for years.

Is this AC current coming over cable line and could this also have caused the HDMI port to go bad.

Google search showed everything to loose ground in the breaker box, bad CATV amp on the utility pole to your house will catch on fire.