i am not sure where the problem lies,,,,somewhere in the edir audit event
cache system i am sure,,,but this has happened to me a couple of times.

remote SLS server hangs for whatever reason,,,,edir will stop processing
sometimes...restarting edir results(at least today) in a ds -255 error. so
kind of throws you off track to troubleshoot.

if anyone is doing heavy auditing and edir stops, or in my case nldap
wouldnt load,,ndslogin returns -255.....check the audit server.

I am not sure why this happens---but just an fyi.