I think I have fixed this: it was a simple matter of unchecking "Update device's date and time" in Intellisync. I noticed after each deletion of Calendar in the BB and resync, the BB's time defaulted to GMT -12, which is odd, given my PC with Outlook is set correctly to GMT +10. When I tried to correct the BB time, all the recurring appts went haywire.
The fix was to delete the Calendar items in the BB, then resync with the update date/time unchecked and it seems to have synced correctly.
I have put this fix in in case someone else has this problem with Outlook 2007.