I currently have Exchange 2003 and 2010 co-existence. I have moved the OAB to the Exchange 2010 server.
Outlook 2007 and 2010 clients when in cached mode do not get updates to the OAB. The error on the server is event id 9360.
When in cached mode it works fine.
I have enabled expert logging and see no other errors accept the 9360 error.