I have a user who is set up with an Exchange mailbox on an SBS2008 server running Exchange 2007. The user has their calendar shared to someone who makes changes to the calendar from a Windows 7 pc running Outlook 2010. The user also has the Exchange mailbox connected to an Outlook 2011 for Mac client using RPC over HTTP as well as ActiveSync on their iPhone. Don't know if this matters as well but the user also has a MobileMe account only syncing contacts on the iPhone to the MobileMe cloud. The problem is that the user is getting duplicate and multiple calendar items in their iPhone and Outlook 2011 for Mac client. From what I've seen I haven't noticed any duplication/multiplication of the calendar items on the Outlook 2010 for PC client, so I believe that it's only occuring on the Mac and iPhone. Any ideas here guys? Would appreciate any assistance.