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.