Ok... it may well be a 4.2.2 problem... but my problem is now resolved following the steps outlined in this BB Support article. The problem described in this article apparently applies to BB Curve and 8830 models with the 4.2.2 software, being used with Blackberry Internet Service. http://www.blackberry.com/btsc/searc...200%2013871738
The problem is that the service book for the calendar is not properly set up, and thus calendar entries are being stored in the device's internal calendar database, which does not sync. For whatever reason, this was causing PocketMac some heartache, and after completing the above process (which requires a Windows system with Desktop Manager to complete), all is now working well for me, even after disconnecting and reconnecting my Blackberry from/to my Macbook.