Outlook 2003 and Outlook 2002

I have a user that was using Outlook 2002 and I upgraded that user to 2003.  She had access to her bosses entire mailbox before and now after the upgrade she cannot access the mailbox eventhough permissions are set correctly.  Another Exec. Admin is able to still access the bosses mailbox just fine with the same permissions.  Iam wondering what in the heck happened?  Should just upgrading from 2002 to 2003 make it so the bosses mailbox can't be opened by a newer version of outlook?  I should also mention that we are running in a full server 2003 and exchange 2003 environment.  Any help would be abppreciated asa I ahve tried everything.  Just ta save you all sometime.  The permission are setup within AD to give this user full control of the bosses mailbox.  Also I compared those settings to the other exec admin and they are setup the same.  The only difference is that one user is accessing using 2002 and the other is 2003.