About Password Changing

Hi,

I have Windows 2000 with Active Directory installed I defined some password policies in it and when my users get this message “Your Password Expires in 10 days” and when they try to change the password they gets error message “Domain Not Available”. They are able to access resources they are able to login but they are not able to change password. I checked my all password policies.I would appreciate if someone provide me solution of it.
Thanks and Regards.
Anurag.