Duplicate calander entries in Outlook 97

On an Exchange network a user has reported recently that after changing a date/time of an appointment in Outlook, duplicate entries have appeared.
Other people are experiencing similier outlook problems.
My question is would the account on the exchange need to be reset / reproduced to remove this problem. And would the calander entries be lost in the process.
What would be the best way to resolve this issue or is it a simple Outlook program issue?