Can't receive email

I have 3 email address with Cox.  A week ago one of them stopped receiving messages.  I spoke to Customer Service 4 days ago and all they could do is tell me the problem is with my machine and not their server.  I have since:

• Verified all settings are correct.
• Uninstalled antivirus and turned off the firewall.
• Repaired Outlook.
• Completely uninstalled and reinstalled Outlook.
• Configured a new Outlook profile
• Bought a new machine and installed a fresh copy of Outlook.

None of this has helped.  What is going on?  Why if I hadn’t made any changes would this start now?  Why are the other profiles not affected?