Well, I recovered access to the site. I found the .htaccess file was altered and the mod_rewrite engine was turned off. I think that happened when I disabled hotlink protection to see if that was preventing the captcha image to show.
However, that did not fix my issue with the confirmation email. Registration of a new user goes fine through captcha and the other tabs. A confirmation email is sent. But, when the link back for confirmation is clicked, an internal server error is generated and the registration is not confirmed. It seems I'm getting closer but I haven't a clue where to look now.