Recipient Update Service - not completing update process

[trmbr]

Just recently, the Recipient Update Service (RUS) on Exchange 2000/SP3, has ceased allocating proxy addresses and also the accounts mailbox. I have checked MS' knowlege base which does list a similar problem but suggests loading a SP3Rollup fix. However I am concerned as it does not list the cause of the problem and the resolution applied. Eg, was there an AD replication issue, a bug in the RUS?
We have 3 AD domain controllers, with the RUS connecting to one. When I checked the mail-enabled users "usnChanged" value and the RUS's "msExchServer1HighestUSN", with which the RUS connects, I found that the users value was higher than the RUS value. According the MS KBA, it states that the RUS will process the account on the next run (Always Run was set) however it never did.
I checked the same parameters on the other 2 AD Domain controllers and foudn that the users "usnChanged" was lower that the RUS' "msExchServer1HighestUSN" number, which according to the KBA, the RUS has processed the account. This is where I am confused as to whyt the values on the 2 AD controllers were lower that the AD controller with which the RUS connects?
I also checked all the AD objects for the user, and all, apart from the "usnChanged" and "proxyaddresses", appeared to indicate the users was mail-enabled.
Is there a white paper which details the RUS process and the AD objects update sequence? I am always reluctant to apply a fix if I dont know the cause and the resolution.
Has anyone experienced the same problem, know the cause, the resoution and/or where there are white papers on teh RUS?
thanks
trmbr

 

[mass2612]

I have seen a similar issue with the RUS not "stamping" the mail enabled users with a e-mail address. I could not find any Q articles but i restarted the System attendant on our system that was running the ADC and it began stamping the mailboxes again.