Update to Invitees (Outlook 2000 SR-1)

I have a user who is set up as a delegate on another user’s calendar. When User 1 makes appointments for User 2 she includes herself as an invitee. However, when user 1 adds information or updates the appointment on User 2’s calendar Outlook is not updating information on user 1’s calendar as well. User is not receiving the send update tab and the invite attendees tab is greyed out.

Any suggestions?