Check out these tips...
Problems with first post.
1) Check if your email has treated the confirmation as junk email. If you are with AOL see the post at the top of the board.
2) 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.
3) One other thing I would do is clear your browser's cookies. In Internet Explorer, click on TOOLS, INTERNET OPTIONS, then DELETE COOKIES.
4) Take a look and be sure the email address you've provided in your profile is correct