[Zope] Site Access Rules and Permissions

Hi, I have the following access rule: <dtml-if "_.has_key('virtual_host') and REQUEST.environ['HTTP_HOST']==virtual_host"> <dtml-call "REQUEST.setURL(path='/')"> </dtml-if> The idea being that if a folder represents a virtual host (see the thread 'REQUEST vraible methods' on this list for background...) you can just give that folder a virtual_host property which the above rule checks for, and if it matches that in the header, if sets the base path to '/'. However, if I try and access any folder with this rule in it, I get challenged for authentication and get 'Authorization failed' no matter what username and password I use, including the root ones! What is going on? Chris