When you are experiencing duplicate contacts/calendar items on a BlackBerry device, please always try the following workaround before wiping or reactivating the device (which is always a risk, because some important personal settings could be lost). This workaround will wipe only the contacts or calendar items and resync them.
- On the Home Screen, choose Address Book (or Calendar).
- Press the menu button and select Options.
- In the Options menu, type rset. (There is no field to type in rset command, type it on your keypad when you get to Options)
- Select Yes in all the confirmation windows that are displayed.