I have a Windows Server 2003 setup as a domain controller with active directory. It's seems to have a problem updating passwords. Even if a user gets a notice when they are logging in that their "password will soon expire, do you want to change it", and they click yes to change it, it doesn't seem to work. They usually start having authentication issues. I usually have to log into the server and go to active directory users and groups, right click on the user having the problem, and reset the password. Then the problems go away.