03-05-2013 02:53 PM
Welcome to the BlackBerry® Support Community Forums.
You may have the BlackBerry Desktop Software configured to Replace all entries on your device with the entries on your computer, see here:
1. Connect the smartphone to the computer with a USB cable and open BlackBerry Desktop Software.
2. Select Organizer from the main menu.
3. Click on Configure... button in front of Calendar.
4. Select the Sync direction to One way to your device only.
5. Uncheck the option to Replace all entries on your device with the entries on your computer.
Let us know if you have any other questions.