Ive got the same problem plagueing me for the past week
driving me crazy.
After some research im kinda thinking its becuase my handhelds keep getting pushed the wrong service books - IE DESKTOP [cical] instead of Blackberry [cical]
ive tried clearing the backup data, deleteing the user account, and wipeing the handheld all at the same time, and that hasnt worked. This started with a fresh install of BES and now ive upgrade to SP5 hoping to fix...
no go...
i had it working on one handheld for one day, but that was it....
Calendar appointments wont show up so that users can accept them, the go straight to the calendar....