[missing-sync-palmos-talk] Duplicate calendar entries after the initial Mac to Treo 650 sync

[winepilot]

I sync the first time with the Mac writing to the 650.  All works 
perfectly, but then on my second sync I get duplicate calendar entries 
on both the Mac and the 650.
I have the latest Missing Sync software.
I am using the USB port to sync between my Mac and my Treo 650.
How do I stop the duplication?
thanks,
-john