First make a backup of BB (and your outlook)
Make the calendar in question the default on the bb (if it’s the Device Default Calendar then all the other calendars service books have to be deleted first) then sync with outlook.
To change the default calender on BB go to options / advanced options / default services / and then change the calendar default to what you want to sync.
To delete the calendar service books go to options / advanced options / service book then delete the calendar service books that you don’t want they look like yourname@gmail.com [CICAL]
If it will not sync then re-set the sync settings in DM and or delete the sync folder on PC C:\Documents and Settings\username\Application Data\Research In Motion\BlackBerry and delete the intelasync folder (close and re open DM)
This next step may not be needed.
Next delete the calendar entries in the BB using DM Backup / restore advanced options. Delete (Clear) all three calender data files calendar / all / settings
If you deleted the calendar service books then Resend service books (to get the calendar setting back on BB). Choose the default calendar you want.
Reset sync settings again (sync settings in DM and or delete the sync folder on PC C:\Documents and Settings\username\Application Data\Research In Motion\BlackBerry and delete the intelasync folder.)
Set up new sync rules and sync with outlook !!!!