Exchange/Outlook 2003: Recurring appointments are getting deleted

One of our users is reporting that recurring appointments are getting
removed from his Outlook calendar without his being prompted. This is
causing problems as he misses meetings that he has scheduled because they
dropped off his calendar. He does sync with a Blackberry but apparently has
it set to Outlook winning any conflict between the device and the email
client, so it is probably not the Blackberry that is causing the problem. I
set up logging on the Outlook client but then read that the log must be sent
to Microsoft to be decrypted. Has anyone had experience doing this?

I am tempted to flatten his laptop and reinstall Outlook, but can’t be sure
the problem is not with the Exchange server so this action might be an
inconvenience to him that does not resolve the problem. Any ideas?