Outlook Calendar items does not recognize previous syncs

[Robert!W]

When I try to sync my 50V (ROM A05) to my notebook, it gives me a Combine/Replace warning that my calendar items have not been synchronized with this computer before, even though I've been using it for over a year. My ActiveSync Calendar options are set to sync All Appointments. It recognizes all other items, Contacts, Notes, Files, etc.

I also sync with my desktop at home without this warning. Why does my notebook act like it's never seen my 50V calendar items?