Unable to fetch item, ID 6287 for multiple users

Environment: EV 10.0.3 on 2 servers, SQL 2008 R2, Exchange 2010 SP2

I'm noticing a large number of errors (~600 across both servers) very similar to this appearing in my event log since upgrading to SP3. (and just 3 entries on one server before that, my logs go back to Christmas 2012).

Coupled with my recent post about permissions not being applied at all to imported PSTs for one user, I can't help but wonder if this is an issue introduced in SP3? We upgraded from 10.0.1.

I found the following TN which mirrors exactly the issue:

http://www.symantec.com/business/support/index?page=content&id=TECH161770

..but as we do not run public folder archiving, there's no tasks to restart. 

The latest person to report a problem is saying she cannot access anything in her vault, and if she opens archive explorer in Outlook, her archive does not appear at all. I've not yet been able to get hold of her to verify 100% what I've been told from my support engineer, but I've got no reason to disbelieve him after seeing 10s of entries in the log saying "Access denied". Using PermissionsBrowser.exe, the permissions /look/ ok. Sample:

So, is there a general issue with 10.0.3 and permissions? When I do get hold of the customer, I'll manually add the permissions to see if it resolves the problem. But as I stated in my other thread, it's not a great solution!

Cheers for any advice, as always.