> Check the USB cable connection in the back of the i1iSis XL. If it's even a little loose it won't connect.
Thank you Doug. That's the first thing I checked, and made sure it was securly plugged into the USB port on the Mac, and even tried different ports. Also tried plugging it into the USB port on my Eizo monitor.
For now, I ran the i1Profiler-full-unistaller again and reinstalled i1Profiler v1.8.1 again. It seems to work for now.
Since the error reference a 'Device instance' i assumed it must to software related, perhaps an i1Profiler link to the ISIS was corrupt or went missing. It was a guess.
I'll call XRite and see what they have to say.