Deleted Calendar entries

[Guest]

-Meeting created by Person A in the calendar and invitations sent out to
Person B and Person C.
-Person B accepted the meeting, Person C rejected. Responses sent.
-Person A modifies details in the meeting such as the start time of meeting.
-Person A sends an update to only Person B
-When Person B responds, the entry is deleted from Person A’s calendar.
Using Outlook 2003, using Exchange server, does have a BES server however
users are not replying from their Blackberry.

 

[Guest]

-Meeting created by Person A in the calendar and invitations sent out to
Person B and Person C.
-Person B accepted the meeting, Person C rejected. Responses sent.
-Person A modifies details in the meeting such as the start time of meeting.
-Person A sends an update to only Person B
-When Person B responds, the entry is deleted from Person A’s calendar.
Using Outlook 2003, using Exchange server, does have a BES server however
users are not replying from their Blackberry.

My main question is why upon Person B responding to the invitation the
meeting is deleted from Person A's calendar? There are no rules in place.
They are using SP2.
Also all permissions have been removed from Person A's calendar.
Has anyone encountered this? Thanks!