Thanks to all those who offered suggestions. In the end it was a strange problem related to the fact that I had another USB Audio CODEC device plugged into the hub (USB record turntable for making digital copies of LPs). Once I unplugged it and reconfigured the IN/Out assignment to follow the Audio Map that WSJT provides, everything worked just fine. So I guess I could say that I now have an "unplug and play" system at least when it comes to using WSJT :) Special thanks to Neal Campbell for helping me sort this out.

73 Rick W2JAZ