Cannot create appointmnet in default calender suing cdo

I am trying to create a appointementItem in the default
folder using CDO 1.21. I cannot do that because when I
tell the folder.messages.Add it throws a MAPI exception.
If I see the count and the maxValue of the messages
object, they both are the same (2 to the power of 32).

Can any one tell me if I can create appointments using
CDO.dll 1.21. If yes what am I doing wrong. Is it some
thing with the Exchange Server 5.5 security setting.
( I can send mail using CDO.dll)

Set myCalendarFolder =
objSession.GetDefaultFolder(CdoDefaultFolderCalendar)
Set myAppointment = myCalendarFolder.Messages
Set myMeetingRequest = myAppointment.Add