External AD Trust randomly fails

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http://serverfault.com – We have a one way external trust between two domains. The trust was configured and validated both ways everything worked fine. Randomly the trust will stop functioning. If we reboot one of the domain controllers the trust will be reestablished. The domains are connected via MPLS circuit. Can someone assist with determining troubleshooting steps? Here are the relevant logs I have found from the trusting domain controller: System- LsaSrv - 40961 - The Security System could not establish a secured connection with the server ldap/dc1.trusteddomain.local/[email protected] (HowTos)