Going into the backup/restore portion of the desktop manager, go into into Advanced and clear your Calendar Databases on your devices. Then run the sync and all should be fine.
Just make sure all your calendar events are in Outlook prior to clearing your Device Calendar, I assume you have a recent backup since you just updated your OS
8830 -> 8330 -> 9550 -> 9650
Just think about how far BlackBerries have come from then till now... And what else is coming.
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