I just setup my receiver including an HDMI output from the HDZone and noticed this behavior. When the receiver's main zone and HDZone were both set to CBL/SAT HDMI input (a DirecTV receiver), the HDZone was getting Dolby Digital, but the main zone was only getting 2-channel stereo. As soon as I switch the HDZone to a different input, the 5.1 DD signal comes back to the main zone. I also verified this behavior with a Blu-ray player including a DTS-HD Master audio signal. When both zones are on the same input, only the HDZone gets the multi-channel audio. Is this a known limitation of the receiver?
Edit: Maybe/hopefully, this was a false alarm. This behavior was happening when my projector (Panasonic PT-AE4000U) was connected to the main zone. After I turned off the projector and left the receiver on, I noticed it wasn't happening anymore. I turned the projector back on; the receiver switched back and forth between stereo and DD a few times, then settled on DD. Also DD to the HDZone from the same input. So, I'm thinking that maybe there was a HDMI sync issue with the projector when this was happening. I'll keep my fingers crossed.
Edited by kklarson - 9/7/13 at 1:35pm