SYMPTOM

• 
  While attempting to connect, I receive the following error message:
  Error 631: The port was disconnected by the user

CAUSE

• 
  The serial (COM) port was disconnected while your modem was dialing. Typically, this is caused by cancelling the dial-up attempt by clicking the Cancel button or closing the dialer window
  

RESOLUTION

• 
  1. Make sure your phone and any other extension connected to this phone line are on the hook
  2. Restart the dialer