Expired password change locks account

We are having a problem with users changing their passwords for logon to our Windows 2000 server. We have Maximum Password Age set to 42 days. When a user is advised that their password has expired, they change their password but are unable to login with their new password. When we check the user's account, it is in an "account locked out" condition. Usually we can just uncheck the "account locked out" box. Occasionally we have to change their password for them through Active Directory.
Our Password Policy settings are:
Enforce password history = 3 passwords remembered.
Maximum password age = 42 days.
Minimum password age = 0 days.
Minimum password length = 8 characters.
Passwords must meet complexity requirements = disabled.
Store password using reversible encryption = disabled.
Our Account lockout policy settings are:
Account lockout duration = 30 minutes.
Account lockout threshold = 5 invalid logon attempts.
Reset account lockout counter after = 30 minutes.
We would appreciate any help. Password changes have become a real hassle!
Thanks for any help!