Problem solved. I added some debug code to my program to track what ports were available on the MC67 terminal. It started out as 5 and then, over time, it went down to zero. That’s when I had trouble. Resetting the terminal freed up the 5 ports again. My guess is that once paired, the terminal locks up a particular port until it is unpaired. My thinking is that it didn’t always unpair properly, or I wasn’t being careful enough to unpair my Bluetooth connection to my Arduino.
The code below generates a simple string containing the ports available. It's not elaborately formatted, but it told me what i needed to know.
//see what local COM ports are available
for (int i = 0; i < m_Bluetooth.LocalComPorts.Length; i++)
s = s + m_Bluetooth.LocalComPorts[i];
statusBar1.Text = "Local Ports: " + s;