With the newer versions of Backup Exec and Exchange 2007, Granular Recovery Technology (GRT), a requirement of the Microsoft Exchange Server MAPI Client and Collaboration Data Objects needs to be downloaded and installed on the Exchange/Media server. Microsoft has updated the Mapi and CDO to 1.2.1 to include Windows Server 2003 and Windows Server 2008. 64bit servers have no problem installing.
Link to download.