Windows 2003 adding server to domain

I am trying to add a Windows 2003 server to an existing network domain which currently has a single Windows 2003 server acting as domain controller. The name of the domain is “ocean”. Currently, the new server is being assigned an IP and is able to see the Internet. However, when I try adding the new server to the Ocean domain, I get the error “The Specified User Already Exists” after entering an account name and password with administrator rights. What could be causing this message? Obviously the user exists, because it could not validate a non-existing user account. I did a search on the Internet for the solution, and the only solution I found that seemed to apply to this was to enter the domain name without “.local”, which is what I was already doing. Any help will be greatly appreciated.