Are you getting these messages in your console log when you make a new user on Mac OS X and then try to ssh in to the computer with that new user name?
Aug 6 12:33:25 example sshd[7296]: in pam_sm_authenticate(): Failed to determine Kerberos principal name Aug 6 12:33:29 example sshd[7294]: error: PAM: authentication error for user from example.com via 192.168.0.1 Aug 6 12:33:29 example sshd[7297]: in pam_sm_authenticate(): Failed to determine Kerberos principal name. Aug 6 12:33:32 example sshd[7294]: error: PAM: user account has expired for user from example.com via 192.168.0.1
Then don’t do what I did. After googling to no avail, I went so far as to completely reinstall Mac OS X. No good.
[Update: Actually, what I did was clone a different system that I had recently set up and used it as the "new installation". Had I done a total, from DVD reinstallation, it would have fixed the problem but I wouldn't have discovered the cause.]
The answer? Make sure you didn’t set the Remote Login preferences in System Preferences/Sharing to “Only these users” and then forget to add the new user to the list!
D’oh.
Hopefully this will help the next person who’s looking for the answer.