When a secure channel fails, ie the trust with the domain has been lost, you must reset it. Most people simply remove the computer from the domain by joining a workgroup, and then re-joining the domain. This is a bad idea because the computer account SID is lost, along with any group memberships.
Type the command netdomm reset MachineName /domain DomainName /UserO UserName /PasswordO {Password | *} where the credentials belong to the local Administrators group of the computer. This resets the secure channel by attempting to reset the password on both the computer and the domain, and does not require rejoining or rebooting.
You could also try the following from the computer that has lost it's trust: nltest /server:ServerName /sc_reset:DOMAIN\DomainController. This also tries to reset the secure channel by resetting the password both on the computer and in the domain, and does not require rejoining or rebooting.
