Wayne,
Thanks for the help. What I don't get is this. If the left channel DSP33 is my "main", and the right speaker gets it's info from this left main speaker, and the right speaker works, how can the fault be the comm to the main? The right speaker, to my thinking would not work if the left "main" had a comm problem.

As soon as I get time, I'll try another main cable as you say. I think I have one somewhere.

G61R, HD621, 3xDSP33 (front, center left), 2xD1500 subs, 2xDSP420 (rears), Sonos everywhere.