Ah, it appears the previously created parent board had screwy permissions. I have set the parent board also to explicitly allow access to all membergroups but guests. (A lot of boards and membergroups were created in the time I was away). If you guys are willing I'd like to try and set it logically for access to "Regular Members" only (not each and every membergroup individually which can lead to this kind of snafu) and see if you all can still get in.