I have a SQL Server running with SQL Server authenticated logins. When I go into Enterprise Manager and try to create a login with integrated security I get the message:
Error 15401: Windows NT user or group 'DOM123smith' not found. Check the name again.

User smith DOES exist in DOM123. I even went over to the domain controller of DOM123, ran Enterprise Manager from there and tried to create the login, and still got the same error.

Does anyone have a clue what is going on?