This is really something you need to take up with Newzbin, I guess, since it's their authentication system. I assume you have the same problems outside of Alt.Binz?
Newzbin really is the worst option for RSS feeds IMHO, and with all of its current 'issues', my advice would be to stay away. Try instead:
http://www.nzbs.org. Once you've logged in, click the RSS link at the bottom and read the instructions for setting up direct downloads. It's automated (no user posts) and has fewer feed customization options, but it has a proper naming system and so is better for Alt.Binz RSS filters. And it's free.