User accounts incapable of authenticating despite SSH working

Hi, folks, first time poster, long-time Mac OS X admin.

I was setting up Snow Leopard Server for a co-lo box that will handle email and DNS and backups, and originally chose the Open Directory option that Apple suggests (at least in 10.6). Since this is a standalone server with really two users, I switch to standalone using Apple’s GUI method after suffering several authentication glitches in modifying user settings via Workgroup Manager.

I created new users and started over, and thought no more about it. All the services worked until today. Then I installed the Java and Safari updates and restarted.

Now, no users except the user I created as part of the setup procedure (which is presumably managed in a separate way?) can authenticate through any method, nor any additional users I create. If I enabled administrative access via Workgroup Manager for those accounts, SSH works with the password. However, no other services (Mail, Address Book, etc.) will authenticate properly.

Any ideas on where to start? There are two entries dated from the last time I changed passwords in /var/db/shadow/hash. I can use the first-created account with its password to access all services, so it’s not a service limitation problem, so far as I can tell.

The error with POP and IMAP over SSL/TLS is authentication error, not “cannot connect.” (Although I found a Mail service configuration problem with POPS in the process that I need to file a radar bug on.)