I'm experiencing a very similar situation with my SR5008. My problem is with my DirecTV. When I power everything up 50% of the time video works fine, but I have no audio. I have to turn off the AVR and turn it back on for it to work. I also have issues where well after start-up, my TV will go black for 2-3 seconds and come back with very choppy video. Again, I turn off the receiver and turn it back on and it works fine. I don't know that this is an issue across the board because have not had the time to watch any blu rays or DVD's for testing. However, I find this unacceptable becuase this AVR will be used with my DirecTV 85% of the time. I called Marantz support twice on this issue. The first call they told me to power on my components in a specific order. TV, AVR, then DirecTV. Marantz service didn't even try to trouble shoot this issue with me beyond the recommended turn on sequence. They didn't even check the video settings with me. Instead, they just offered to send me a new replacement, which I found surprising and odd.
On another note, I contacted Accessories 4 Less, who I bought this unit from. They said that they have fielded this issue many times and found that low quality HDMI cables are the culprit and recommended I purchase better cables. I found this a bit ridiculous, but they were rather certain.
Once I receive the new AVR I will see if the problem goes away. If not, I guess I'll try new HDMI cables. Does anyone else have any experiences with this sort of issue using a Marantz or other brand of AVR?