[afremont]

Also - do you have a suitable HDMI Clock Limit entry in your config.txt - I found that stopped my Onkyo AVR dropping out to black.

(Or is this no longer required popcornmix?)

Yes, if afremont confirms that avoiding "adjust PLL" avoids the issue, then hdmi_clock_change_limit would be my next suggestion.
I use "hdmi_clock_change_limit=40" which is needed by my Onkyo 609.

Okay, I confirmed that avoiding Adjust PLL avoids the issue. I put this parameter in config.txt, right?

EDIT: I put the hdmi_clock_change_limit=40 in config.txt, rebooted and went back to adjust PLL. Seems to be working okay, but I've only tested it for about 60 seconds so far.

I love my Onkyo most of the time, but they do seem to have a couple of quirks. I have a 604 that hated uVerse audio when it was DD 2.0. It would have the most annoying dropouts, but only with DD 2.0 stuff. Finally dumped all that pay TV stuff and went with OTA and streaming. Best decision of my life. So far, I love my TX NR-828 though it would be nice to drive 9.1 speakers instead of only7.1.