Please name your display model. For instance, previous Panasonic plasmas had FW released for the specific issue of Onkyo compatibility.
The FW release does not currently state it, as it's now a newer FW I believe, addressing new issues, such as Amazon streaming. I am speaking of the models such as G10, G15, V10, etc.
Is the bluray player's FW up to date? It probably doesn't matter, but I am curious.
If the display is not a Pana, you can confirm TLS' suspicion of the Onkyo by trying a different BDP. Using a cable box is not conclusive evidence to me.