If you didn’t already read it elsewhere, we’re going to be changing the news.mozilla.org domain name to point at the Giganews servers in the morning (PST) on Monday, January 9th. The message pointers are different, so if you read the newsgroups via NNTP (rather than email), you may need to unsubscribe and resubscribe from each of the groups after the change is made in order to get your “last read” pointers synced up. If all of the new posts start showing up as already-read to you, this is likely what you’ve run into.
For more information, see the News Migration FAQ.