mm what are you trying to do? As a general security rule, I do not permit guests onto my Moodles, ever. Not sure why anyone would want to, unless someone wants to use Moodle to sell a product.
Many of us use part of our Moodle sites as open web pages for the public. Moodle has come a long way. It is part web site AND an engaging course site. Surely the question should not be why? but why not?
Anyway. Has the problem been solved anyone?
Well I can't answer for Sue but although there has been a problem with some people getting guest access due to duplication in the database entries (for which there is a solution)for the vast majority of Moodle sites of different version, guest access works just fine. My school uses Moodle (1.9) as their website and the School demo Moodle http://school.demo.moodle.net/ is all guest access and that works fine too.