Unable to start Task Scheduler service

I am running W2k sp4 & receiving error when starting the task scheduler service “could not start the service on local computer, error 1717 interface unknown”

This has been running ok in past, but as no additional software or config changes been made at a loss as to why will no longer start. Machine on windows 2003 domain as do at least 20 other W2k clients & this is only Pc with this error. virus scans are showing as clean

cheers, Steven.