Andrew Everard:
See, I'm now wondering whether this has something to do with it:
In other words, the receiver is detecting the signal source when viewing menus - which will in all likelihood not be DTS-HD - and setting itself up accordingly, then not switching surround mode when the signal unlocks from that input format for a second as play begins, then comes back as DTS-HD.
May be clutching at straws, but this would seem to give some explanation of what you're experiencing...
That all makes sense, Andrew, and I agree it's what I am experiencing.......is this taken from the Sony manual? Can't find it in the Denon one, so assume so?
Your assumption that the menu's are not DTS HD is spot on too......what will sort this out then? Changing this setting?