alfa21 0 Newbie Poster

Hi all,
I have a porblem in my Mail Server using Exchange 2007 SP1. Yesterday after I restarted service MS Exchange System Attendant, I started receiving an error in Application Log in Mail Server. Error is:
Calendaring agent failed with error code 0x80150856 while deleting appointment,
or similar depends whether I add or delete an appointment from any Client. The Appointments are created or deleted without any problem, only this error is written to Application Log. I googled a bit, and some people writing about Public Folder Database Permissions of System Account. I used EMC of Exchange 2003 only to view permissions, and I realize that both in Mailbox and Public Folder Databases, SYSTEM has only special permissions, not FULL. I don't know whether is OK with Exchange 2007, or if not how to add permissions to a database.

Thank you in advance for any help