I have the Blackberry Desktop Manager installed on both my desktop and laptop computers with the manager configuration identical on both. My MS Outlook (PST files) is identical on both.
When I sync my BB 8330 Curve on my desktop it works fine. However, when I attempt to sync my BB with my laptop it attempts to add or change a number of old (already synced) calendar, address book, and task items.
It appears that there must be some other BB desktop manager configuration file that is not identical on both computers - thus causing the laptop Desktop Manager not to recognize that the items have already been synced.