Girlinflorida-
It looks like your registration was completed successfully... Do you log into the site, and then get the "unregistered" message when you try to post?
If so, your login may be timing out before you submit the post. In your User Control Panel settings, under User Options, there's one setting called "Automatically login when you return to the site? (uses cookies)". If you select YES to this parameter, you shouldn't get logged out during your session.
Give it a try, and let us know if that works for you.