All I can tell you henry is that on my SD box, I could have sound out of both at the same time and there was no delay. These HD boxes seem to be junk. The installer even told me not to use HDMI cables that Verizon wont support them becuase the HD box is hinky with them. No HDMI cable for HD??? REDICULOUS!!!!
Eric, What is your current setup? Are you using component from the STB to your receiver and audio outs via composite, from the receiver to the TV?
The only reason I said they should not be used at the same time is based more on the concept of mixing speakers than of causing a delay. I don't use both at the same time because I have good AV speakers and the TV sound quality isn't nearly as good because they conflict.
If you let the AV receiver control the audio with the setup in my initial question, there should be no delay.
I do not doubt your issue. I only use my AV system, not the TV. To try to replicate your problem, I just set mine up with composite out from the STB to the TV. There was an obvious hollow or echo effect, I then connected the composite from the AV receiver to the TV. The hollow echo sound went away. Obviously you need to sync the TV and the AV receiver if you use both so one doesn't overwhelm the other. Do you have a center channel speaker?
I can't add any more because I either use TV only for sound or my AV receiver but not both. I know there is a delay in the HD box. If you have a SD box in one room and an HD box in another, there is a slight delay between them. Your issue is different. If you tried running the sound to the TV from the receiver and still have your issue, maybe another poster will have a suggestion.
It is likely your HDMI connection. I had the same problem. Switch to a component cable connection ( red , green, blue and audio red , white).
Apparently the motorola HD STB has issues with the HDMI connection and verizon is working on fixing it - not soon the guy told me.
Hope this helps. Good luck!