Hey folks, this issue auto-magically healed itself. What did I do to resolve it? Good question 'cause I'm not sure! It all started working again once I plugged both my 1642AI and StudioLive SIII 16 into my computer at the same time. Go figure! :-)
I just updated my 1642AI to the latest firmware - v11979, and poof! everything has disappeared from UC. UC does not recognize/see my mixer. WDM Setup says "WDM Setup is not available for the connected devices.". Device manager does see "PreSonus&STUDIOLIVE_1642_mk2" under Other Devices. The Sound window does not see a Presonus device, only the default Realtek stuff. UC is running latest and greatest version. I'm running W10 Home using an i7, 32gb ram, 5oogb SSD. Please help, I'm totally mystified as to what may have happened.