public calendar share view incorrect for one user

Have a problem where one client has a few extra items showing on his view of
the public calendar that several of the users are using. I would like some
pointers as to where to begin looking to see if I can determine why this
view is only different for the one user. He is accessing the Exchange
server via a vpn connection and using Outlook 2007. I was wondering if it
has something to do with his profile on the server or if there is an
incorrect copy of the public calendar being cached on his machine ?

thanks in advance