OMG - I found the solution!

Inside the Meridian Program, under "View" was something called "Options". I clicked on that and it gave me a choice of COM ports to use! I picked COM3 ... and everything worked.

Halleluiah! I'm leaving these last two posts in for anyone else whom it might help in the future.

EDIT: OK - I feel dumb. The part about View/Options/Select Com port was actually in the 561 manual. I just skipped over it. crazy

Theater: 565/562v, 519, Analog speakers (NHT & Velodyne) Pioneer LaserDisc, Sony PS3, Comcast Cable
Office: 561, DSP5000.2, NHT rears, Acurus Amp, Technics Turntable, Sony SACD Changer, PC Digital out