Has the Thunderbird user interface changed recently? i.e. the Reply button? I'm sure I used to click that to reply to posts in newsgroups but now it sends a reply to the email address of the poster instead. I don't remember having to hit a "Followup" button before?
It is annoying. I keep forgetting this "Followup" button and keep accidentally sending email replies to posters instead of to the newsgroups.