FYI.
“The Comcast Newsgroups service has been discontinued. We apologize for any inconvenience. If you have already signed up for Comcast Newsgroups, please be aware that this service will be discontinued on 10/25/2008.”
A list of links to Public news servers
And (for a price!) by-golly! Giganews (which had been providing Usenet services for Comcast) will provide service for you too!