Not able to accept the reschedule request in the calendar

Please help!!!I got a meeting invitation and i accepted it. but the updates send would not get updated. Once i open them (in fact got a error message saying that the update i was trying to open could not be executed because the original invitation was not identified- once i said ok to the error message then the meeting update opened but i was not able to action any acceptance options in the update message)

please let me know what is wrong and how to fix this bug