MTU responded to my support ticket and a beta version fixed the error (without installing a new sound card)
BTW, I think the problem is that on my computer there is a sound program installed by the sound card company called "Realtek HD Audio Manager". Anyway, the point is that this program senses when different connectors are plugged into different jacks and when it didn't sense a mic plugged in it told the OS that the mic wouldn't work, which caused the error messages. At least that's the best guess...
A quick/easy solution was to plug in a connector to the mic input (any connector, even without a mic on the other end) and the error went away because the program "saw" a connector connected to the mic input...weird.