We have a number of WSS sites created under a MOSS portal site. When a
non-administrator tries to connect to one of these sites, they receive
an "Access denied" message page. If they go back and try the site
again, it allows them access.

The users are members of the out-of-the-box "Visitors" Sharepoint group
for that site, which has only one member, a security group in AD, of
which this user is also a member.

Has anyone encountered anything like this before? Is there another
right I need to grant the "Visitor" Sharepoint group?