Matt - I'm still stumped (could be me). In normal display mode - no issues with audio over HDMI, but in Theater Mode the problem persists. On the main screen, moving between the menu items, no issues. When I select a sub screen, or move between icons on a sub screen - the audio over HDMI turns off, then on again - I can see and hear the amp reseting to the new stream. The video is rendering fine - no issues, so not thinking video is the problem. I may have inadvertently mis-configured something, but I can't see anything that would cause this, especially when no audio is playing. Again - 2 channel music and multichannel movies sounds fine when they are playing - this is an idle problem.
Any ideas or guidance much appreciated. I could try a different amp, but that's a last resort hassle, and at this point I have no reason to suspect it - the HDMI audio is working fine from 2 other devices.
Thanks again.
jeff