Recently we moved from an Exchange 2003 to Exchange 2010. Since then we've discovered an issue with delegates not receiving meeting requests correctly for their managers and although we have a ticket open with MS, I did some googling around and found this old chestnut from OL97. Same symptoms, different email client (we are running Outlook 2007).
I'm poking through ADSI edit right now to try and gain a footprint.
Thanks for any input