Hi ace2701,
I am not too familiar with these settings, but from what you have described, avast! looks to have detected the newsgroup, and is trying to provide SSL, when it is not wanted.
Now this is a bit of a guess, but maybe you could try this:
Open avast! GUI --> 'Real Time Shields' --> 'Mail Shield' --> Expert settings --> 'SSL accounts
Is the NNTP setting displayed there? If it is you could try setting the encryption to none. (as that seems as though that is what the newsgroup server wants...)
-Scott-