Turns out the issues I mentioned in the previous post which we thought were affecting users with different client versions of Outlook are actually affecting blackberry users on the Exchange 2003 server only, regardless of outlook version.

To clarify, users with blackberries on our exchange 2007 server are having no issues. Those on the Exchange 2003 server are getting duplicate meetings when they receive an updated meeting request. And if the meeting is cancelled, it still leaves one of these meetings behind on their calendar and removes the other. This began after we upgraded the BES server to the newest version and registered the cdo.dll and installed the MAPI for Exchange 2007.

Users without blackberries are not affected.