Thanks Chuck, that took care of the guest problem. Have one more problem though.
In order for a usergroup member to receive the category permissions I have set for that particular usergroup, the usergroup has to be set as the member's default group in phpBB. Any ideas to get around that?
This not a new problem. It's just something that never mattered before because our permission requirements were pretty simple and as I stated above, our other site has no problems with what we're trying to do with this one.
Sorry, it's a 9 year old forum that's been upgraded & modified over the years. That might explain the non typical usergroup numbers.