Thanks Larry, but I don't have a center channel, as far as I can see. But, this incident also causes me to wonder about all the possible variations of discs that may be out there, most probably recorded in stereo, but also possibly some odd-balls, with music on L channel and voice on R channel.
I also wonder about that one rental DVD disc that I have. 'Scene 12' has full stereo, but all the other 'scenes' just have noise and very low level sounds that are unintelligible. What could possibly have happened to this disc to cause loss of audio on the first 11 'scenes' but not on the 12th? When I send it back, I'll mark it defective.