I've looked at other answers to this problem but they seem to relate to multi server environments or new migrations - neither apply here. The Exchange 2013 server was implemented last year as a migration from Exchange 2007. It has been running well since. I upgraded to SP1 on Sunday night and since then all users, regardless of Outlook version, are continually being asked to "the microsoft exchange administrator has made a change that requires you quit and restart outlook". Clicking OK loads Outlook normally (no restart). I can delete the Outlook profile and set up a new profile OK but the issue comes back again. Deleting the users roaming or local profile does not help either.
The CAS seems to be set correctly - when I run Get-MailboxDatabase | fl RpcClientAccessserver it returns the correct server.
There are no public folders set up.