I didn't think the NTL newsgroup servers were ever alive in the first place
Could be something wrong with the DNS servers you are using, the path to them, or you specifiying them in windows.
Anywho, news.cable.ntlworld.com resolves to 80.5.182.99. Just substitute it instead of the host.
If you have the same problem, you can do a search from dns lookup or reverse dns, in a search engine, and resolve them yourself. Even if the server is down, the host should still resolve to an IP.
Edit: I have just tried connecting to the NTL broadband newsgroup server, works fine here.