HTTP_REFERER

Hello. when I try to add or remove a forum/category forum give me an error:
"Bad HTTP_REFERER. You were referred to this page from an unauthorized source. If the problem persists please make sure that 'Base URL' is correctly set in Admin/Options and that you are visiting the forum by navigating to that URL. More information regarding the referrer check can be found in the PunBB documentation."

I have checked the 'Base URL' in Admin/option it is correct!
How I can resolve this problem?
Thanks a lot!