This is the page Comcast displays when you enter an invalid username and/or password:

The page cannot be displayed The page you are looking for cannot 
be displayed because an invalid method (HTTP verb) was used to attempt 
access.

Please try the following:

    * Contact the Web site administrator if you believe that this 
      request should be allowed.
    * Make sure that the Web site address displayed in the address 
      bar of your browser is spelled and formatted correctly.

HTTP Error 405 - The HTTP verb used to access this page is not allowed.
Internet Information Services (IIS)

Technical Information (for support personnel)

    * Go to Microsoft Product Support Services and perform a title 
      search for the words HTTP and 405.
    * Open IIS Help, which is accessible in IIS Manager (inetmgr), and 
      search for topics titled Setting Application Mappings, Securing 
      Your Site with Web Site Permissions, and About Custom Error 
      Messages.

I didn't even realize that's what it was, until I noticed the URL had "&errorMessage=Invalid%20User%20Name%20or%20Password" in it. You'd think someone working there would be somewhat "good with computers". Oh, sweet feathery jesus.

This has been going on for at least a week... and probably longer.