Adding Users

On our new 2000ad domain I can not manage computers from AD. Also I can not add users at a 2000 workstation from the Domian. Even with proper rights. The Message we get is can not locate domain. Note we can All login and see each other. and share files. I believe its something to do with DNS. Sometimes when you go to add a user the drop down arrow is available sometimes it’s not. Any suggestion would be appreciated.