My environment: Exchange 2007, Outlook 2007, fully patched.

Situation: 5 secretaries are dealing with meeting requests for 10
executives. Secretaries are grouped under an AD user group. On the
executives' calendar object, we grant "editor" rights to this secretary
group, instead of setting delegates.

Goal: all 5 secretaries can prepare meetings on the 10 executives' behalf.
There is no need to map which secretary serving which executive.

Problem: Secertary-A prepares a meeting on Executive-1 behalf, inviting
Executive-2 and Executive-3. The meeting requests are shown on the three
executives' calendar. Then after a random period of time, the meeting request
disappears from the attendee's calendars. This doesn't occur always. And the
meeting request may disappear from one (only Executive-2) or all attendee's
calendar (both Executive-2 and -3).

Question: 1) anything wrong at the settings? 2) what possibly would cause
the problem?

This is extremely difficult to trouble shoot as the problem appears in random.

Thanks in advance.