The latest nightly fixed the login problem for those with an uncompatible PHP-version. If however, you're in the middle of the upgrade you can't request a password reset. The solution is to hack ZP to allow you to log in and perform the upgrade. Then you can reset the password and continue on happily.
In auth_zp.php change line 43:
`zp_setcookie("zenphoto_auth", md5($post_user.$post_pass), time()+5184000, $cookiepath);`
to:
`zp_setcookie("zenphoto_auth", md5($post_pass), time()+5184000, $cookiepath);`
In functions.php, the checkLogon($user, $pass) function. Change line 2077:
`$md5 = md5($user.$pass);`
to
`$md5 = md5($pass);`
Now - log into your database and set the admin password field to any of the checksums above and you'll be able to login with the corresponding number as password. As soon as the update is complete; undo the changes, log out and request a password reset.