Any idea is welcome at this point, I appreciate it. I just tried everything again, and after disconnecting and re-connecting the audio cables from Oppo to receiver, I am now able to get sound from the SL speaker, but not discretely. When a test tone is sent to the SL speaker, I get sound from both the SL and FL speakers. Just like the right now. And a test tone to the center speaker is giving me sound in the center, AND both FL and FR speakers. What the hell? To summarize, with the problem channels bolded. FL - sound comes from FL only. Center - sound comes from FL, Center and FR. FR - sound comes from FR only. Sub - sound comes from sub only. SL - sound comes from SL and FL speakers. SR - sound comes from SR and FR speakers. I wonder if something got fried. There were some power outages a few weeks ago, but just brief outages overnight. Everything is connected to a PS Audio Dectet AC Power Conditioner.