Don,
Thanks for the reply. It seems that there are two distinct problems here.
1. The issue with the permissions seems to have been related to moving an instance of the photo album to a new url. I had in in one place on the site map, and then created a new place, mounted the instance on the new place, and then deleted the old url node. This process seems to have screwed up the permissions. Maybe there is some residue of the old url key stuck in some table somewhere? I tried setting up a new instance of the photo album and it works fine. One other clue is that if I delete all albums in the problematic folder, the public can get at the folder, but as soon as I added an album (even with public read perms) neither the album nor the folder were available without logging in.
2. The issue with the registration is a real nuisance. What is happening is that after logging the user in, the browser is redirected to the login page again, which gives the user the impression that the login has been unsuccessful. In fact the login has been perfectly successful. Can anyone help me to sort out a workaround so that the redirect can be avoided?
Richard