What you quoted gave the answer:
I have the Audio Output Setting set to "Digital Out (Optical)" with both DD5.1 and DTS 5.1 checked on.
I probably could have been more clear:
Settings => Audio Output Settings = Digital Out (Optical)
The settings seem pretty straight forward. I'm trying to see if others have the same bug, or if this bug is somewhat unique to my console (in which case I'm returning it). I see no evidence that the TV is having an issue (though I have the speakers turned off, so it shouldn't warn me about an incompatible audio signal).