Help is problem processor or BD?

I have an Integra DHC 9.9 connected to a Panasonic BD55 via HDMI. It has worked flawlessly until now. Today when I tried to view a BD disc, I get video but no audio. The Integra faceplate says Full Mono and can not be changed to any other surround setting. I inserted a CD in the Panny, and audio is working fine with it, and it correctly reads audio format as all channel. Is this a processor or BD problem? Any ideas on what the problem is and how to fix it? Thanks in advance.
It's not the disc. Tried several BD and no audio on any. Put in CD and get audio. Get audio frim cable/sat also.
Is the audio of your BD player in True DD or DTS. I think only HDMI 1.3 can carry it. Is your Integra 1.3 compatable? You may have to be in regular 5.1 audio and not True HD.