You are the administrator for a large single-domain network. You have several Windows Server domain controllers and member servers. Your 3,500 client computers are Windows workstations. Today, one of your users has called for help. It seems that his computer is reporting that a trust cannot be established between his Windows computer and the domain controller. He is unable to log on to the domain. You examine the computer's account using Active Directory Users and Computers, and there is nothing obviously wrong. You need to allow this user to log on to the domain. What should you do?