Question : OLK2007: Cannot update the appointment because the corresponding item in the folder you synchronised does not match this item

We have a few people in the office who are getting duplicate calendar entries using outlook 2007. When accepting a meeting request/update, they get the error "Cannot update the appointment because the corresponding item in the folder you synchronised does not match this item. To resolve the conflict, open the item." when opening the item Outlook shows 2 identical entries with same time stamps etc. At first, some searching on the web suggetsed this was a issue when requests were coming from people acting as delegates but at least one person is getting these symptoms when recieving invites from people who do not act as delegates. Searching also found similar problems for versions prior to 2007 and they suggested turning off cached calendar mode but this is not applicable in 2007. only our 2007 users are experiencing this problem.
Thank You for any light you can shed on this problem, i can see from searching for a solution that there are many, many people out there with this problem but it seems no-one is able to find a solution.
Ryan

Answer : OLK2007: Cannot update the appointment because the corresponding item in the folder you synchronised does not match this item

Could this problem be caused by BES?
Do you have BES fully patched?

Also make sure all instances of the exchange install are at the same version.