In my opinion running RCA cables is not a fix, it's a work around. It bugs the hell out of me when I can't get something to work. I have an Oppo 980H connected to my Denon 3808CI and I have no problems playing audio CDs, but I have my Denon connected to a TV not a projector.

Check these settings on the Audio Setup Page on the Oppo:

Digital Output should be set to Raw
HDMI Audio should be set to Auto
SACD Output should be set to DSD