I have recently been having a problem with a couple of my VIP users and their calendars. The problems seem to be restricted to modifying a single instance of recurring appointments (i.e. move, expand, delete the instance). It does not occur every time, but is intermittent. The appt. change is performed and appears correctly in Outlook, but is either duplicated or does not appear in the HH.
I worked with RIM, and they told me that this is a known issue in Outlook and the way it handles recurring appts. Each appt is assigned a unique ID, and when changes are made, sometimes another ID is created (hence creating a duplicate appt in the HH), or it is 'ignored' (hence 'blinding' the HH to the change). Their advice was that the issue was fixed in Office 2003 SP2, and that I should upgrade the users to that version. I've done so, and am now waiting to see if the problem reappears.
I hate to muddy the waters further, but that's what I've been told. There's obviously a major issue here, and I'm going to try some of the recs here to try and address things from the server side. Thanks, all!