Use DM to delete your calendar databases on your Pearl to start clean...typing this from memory, so I may be a bit off.

Launch DM and go in to the Backup utility, and click Advanced. A dialog will open showing the databases on your PC and on the Pearl.

Find your calendar datatbase on the list on the right (there may be two - Calendar and Calendar All). Select them and choose the Delete option to delete them.

Then try to sync.

That's worked to solve any sync problems I've had w/the Pearl.