Purge agent in Resource Reservation

HiFew months back i have upgraded the domino server from 6 to 7,I have also upgraded the design of resource reservation.But the purge agent of this database is not working.when i tried to run the agent manually it is giving me error “Document already exist in collection”

on this line

Set dcProf= db.GetProfileDocCollection(“CalendarProfile”)

Can some one guide me how to resolve this.

Regards

Dali