Has the guest user also been assigned access to the content that is being served up?
Yes, but in our production environment now I'm seeing even stranger behavior. For example, I select at the server level to turn on guest access, but don't have the option to turn on/off guest access at the site level. I'm going to open a ticket as well because the behavior is not at all what I expected. When I try to add a guest user to the project it allows me to select the Guest user and set up the permissions, but when I hit save the user GUEST disappears.