My calendar synchronization developed a problem when Outlook went crazy on my computer. Basically Outlook would refuse to synchronize with my V3. I was able to solve it by using Motorola’s mobile PhoneTools software.

From the main screen
Menu > Organizer > Mobile Phone > Backup/Restore
OR
Open the Calendar
Tools > Synchronize > Backup/Restore

Just go through the menus and select the options to delete the calendar data from your phone. After a minute or two of processing your phone’s calendar should be empty. Now you should be able to re-open Outlook and sync the data.