Issue Resolved!

First, I tried shutting off power from the switch on the back of the unit. I switched it back on after 30 seconds and this made no difference.

Next, I unplugged the unit for about 10 minutes, then plugged it back in and pressed the power button - everything was back to normal!

Also, last night I received an email from Outlaw Customer Service. They had read my post and suggested that I fool around with the Source Selection buttons just above the volume control. Sometimes one of these will stick in, causing what happened to me. I replied, thanking them for the help - that is awesome customer service!