Change password on start

On a single system on a 500 user network, every time NT4 is started the message "your password expires today, would you like to change it?" appears. A password change is accepted but the next time NT is started the message appears again, the user may also cancel the message with no ill effects. This is true for any authorized domain user that logs on to this one system. When logged in with admin priviledges to the server user manager program, any account that is opened for inspection has the "user must change password at next logon" block checked. The user manager program, when opened simultaneously on another system shows the same accounts as normal.