The error is on the admin side of the site. You can't view it (but you can see the errors in the bottom of the quote in my OP) so whether the forum is publicly accessible or not DOES NOT MATTER. If you're not going to figure that out, please go away, and let someone else provide useful assistance.
edit2: The website is accessible just fine for everyone. PunBB, however, is not installed on the public site anymore. When software has bugs, I remove that software until I can fix the bugs. How hard is that for you to understand?