Google isn't intended as a news server. It is possible to use it that way to read RGG, but that's not what it was designed for. It's an archive, just as DejaNews was (That's why X-No-Archive makes posts invisible in Google Groups). If you want full-featured USENET browsing - including unarchived posts and killfile options - you'll need an NNTP server and a capable newsreader such as slrn or tin. You can find NNTP servers for low fees ($5 or so a month), plus there are always a few free ones (though their group propagation is fairly poor). Your ISP probably offers one, as well; try setting the 'server' portion of your client's configuration to news.myisp.com, or somesuch.
Suggestion: the usenet server http://news.individual.net/ is cheap and very good.
unkx80: For Windows users, the built-in Outlook Express already provides newsreader capability.
http://www.eternal-september.org/ is a free news server (text-only/no binaries).