I see some other posts here mentioning login problems following site updates to the most recent v1.4 release. I have also noted the responses denying any changes to zenphoto itself that might cause such a problem. Nevertheless, the same thing happened to me when I ran the setup to update from version 1.3.1.2 to version 1.4.
I was able to log in as the administrator both prior to the version update and for initiating the upgrade process. Following that process, however, I was locked out. In fact, the reason appears to be a change made during the upgrade to the extra_auth_hash_text entry in the zp_options table. I certainly didn't change it myself.
Here are partial direct dB exports of the zp_options table before and after upgrading. Note the change in the entry for extra_auth_hash_text from `& amp;` to `&`
Before upgrade (v1.3.1.2):
`(1, 0, 'zenphoto_release', '5831', NULL),`
`(2, 0, 'extra_auth_hash_text', 'T^Y|O9upranHBI6F#4Z?VPlMxSA& amp;,+', NULL),`
`(3, 0, 'libauth_version', '2', NULL),`
After upgrade (v1.4)
`(1, 0, 'zenphoto_release', '6454', NULL),`
`(2, 0, 'extra_auth_hash_text', 'T^Y|O9upranHBI6F#4Z?VPlMxSA&,+', NULL),`
`(3, 0, 'libauth_version', '3', NULL),`
NOTE: The space in & amp; is because backticks here won't let it stand intact as it actually was in the database.