Outlook Search result won’t open email

Scene: Outlook 2003 SP1 Client on Exchange 2000 which is on a Server 2003 box.

User1 has granted Delegate permission to User2. User2 can open User1’s mailbox, open her mail, file it, etc. If User2 uses Find to search User1’s inbox, the search results display, but User2 gets an error attempting to open or access the found item. “Cannot open this item.”

Where does this supposed permission problem lie? User2 has admin rights to her PC.