SYMPTOM

• 
  While attempting to connect, I receive the following error message:
  
  Error 645: Internal authentication error

CAUSE

• Older Prodigy Internet V1.x Kits
• Conflicting Software or Incomplete Software Setup
• Improperly configured Dial-Up Networking and/or Network Components
  

RESOLUTION

• Older Prodigy Internet V1.x Kits
  Prodigy Internet V1.2.10 and lower Kits may experience this error. It was fixed with version 3.0.0.75 of Prodigy Internet which is designed to work more smoothly than previous versions. Upgrading your Prodigy Internet software often can correct the error. To obtain the latest Prodigy Internet software, go to: http://www.prodigy.com
  
  Conflicting Software or Incomplete Software Setup
  1. Close any unnecessary communications applications and ensure all fax software is disabled and not in an "auto-recieve mode"
  2. Restart your computer to make sure that any recent configuration changes have taken effect
  
  Improperly configured Dial-Up Networking and/or Network Components
  If restarting your computer doesn't solve the problem, then:

1. Check your Dial-Up Networking configuration
2. Verify that your Dial-Up Adapter is configured to use the necessary TCP/IP protocol