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Try this (same deal happened to me recently): Make sure the correct email address is set to be the default on the BB Calendar (Options > Advanced > Default Services). Select your email address if you have more than one.

Make sure your Outlook calendar is complete and up to date, and follow the instructions in How to Clear/Delete all your Address/Calendar items at once - BlackBerryFAQ

Confirm on the BB that the correct email address is still set in default services.

And resync.