Have been searching this for a while.
I too have problems with the 6412 - green screen.
I have not checked my firmware in about 6-8 months - have been using component.
I will be trying HDMI tonight and checking firmware, and also trying changing the color space.My big problem is my DVD-5900
But I also get green screen with DVD-5900 passing through my AVR-4806.
The DVD-5900 does not have HDMI, so I am using a DVI-HDMI cable.
So my question was could it be the 4806?
Sent it back to Denon - they sent a new one - same problem - green screen
I can understand the problems with the 6412 - lots are having same issue.
But how can a Denon product not work with another Denon product?
I have tried to think of everything - could it be because the 5900 has DVI instead of HDMI - but they are supposed to be backward compatable....
Could it be the TV??
I will post a follow up when I try the Moto box - it is Cox and area is Rhode Island.