First I visited the site, saw the large SIGN UP NOW button and pressed it. I was prompted to enter my username/pw. The "Do you already have an account? yes/no" part was missing, so I entered my desired username/pw thinking that would start the registration process. Instead I receive the error "The requested user cannot be found" and then am prompted to "Log in or Sign Up".
I tried several things not sure what was wrong and ultimately, I entered a username and left the password field blank. It was then I received the "New registrations are currently not being accepted" message.
I would suggest when an admin selects to not accept registrations that the SIGN UP NOW button be removed from the forums. Also adding a "not accepting new registrations" message would probably be helpful at the login screen where a user enters his or her username/pw.