Screen flickers on / off when run through receiver. I have an Onkyo TX-SR605 that I just purchased

Question

I have an Onkyo TX-SR605 that I just purchased and have connected it to my Panasonic plasma TV. When I'm watching standard TV (cable box connected to the receiver via HDMI input and the TV is connected to the receiver via HDMI output)the picture looks normal but then it will black out for a second or two and then come back on ....be fine for a 10 seconds or so and then black out again for a few seconds. Then sometimes it will fade in and out fairly quickly. But when I play a DVD it doesn't flicker. Both HDMI cables worked fine prior to the install...maybe they crapped out that's all I can think of....and advice