If you have a very new PC with USB3 ports, try connecting to a different port, preferably USB2 because hardware /driver support for backward compatibility of USB3 varies between manufacturers.
This certainly explains why the radio worked properly on the laptop, which only has USB 2.0. It also explains why it worked when I put it back on the big computer. Just for the sake of testing one new variable, I had indeed tried a different USB port, and one known to be 2.0 only.
And so we have cleared that up. I figured it was something to do with the USB, since there have been other issues with other products used for radio. Obviously, this is not a bug in the Excalibur Pro, which in fact is living up to its advertising.