I had the same problems with my 4806, turns out the receiver was broken and needed some type of HDMI upgrade or something.
In it's absence, I bought a Denon AV 897. For the money it's a great little receiver, and very powerful. It drives the Axiom's with no issues whatsoever.
The HDMI in and outs work fine on this one, but I did have to do a little fiddling with the set up.
First, I set my satellite box to receive "ALL" signals
(720i, 1080i, etc.), and then I made sure the "Native" feature was turned off.
Now to the Denon. Here, I set the "HDMI in ASSIGN" to whichever input you're going to use (I use the DBS function), then I set the "Video Convert" for the DBS to "OFF". You do not want to down convert the HDMI signal here since it is already HDMI. Finally, I set the "HDMI Out Setup" to on for my other component connections that do need to be converted.
That should do it for you. If not, call Denon. Your receiver may be broken also.
Good luck!
Tab