MTA error with Exchange 5.5

I keep getting this warning from event viewer and cant figure out how to fix it.
An RPC communications error occurred MTA. Unable to bind over RPC. Locality Table (LTAB) index: 5, NT/ error code: 1753. Comms error 1753, Bind error 0, Remote Server Name ULPDC1 [MAIN BASE 1 500 %10] (admin