Outlook appointments are disappearing, but they still display on the phone

Hi,

This morning, I had a user report that his calendar was missing several appointments.  They're visible on his phone, but they're not displayed on his Outlook calendar (Day/Week/Month view is prevalent, but some of them I don't see in any view).  As the day progressed, I got four more reports of this issue.  They all sync their phones with the Exchange server, but that's the only common thread I can find.

Several of them also noticed that they cannot dismiss their reminders.  They receive the error "Cannot turn off the reminder. You may be reminded again."  If you try to open the item for the reminder, you get "Cannot open the item for this remidner. The end date you entered occurs before the start date."

When I was searching for the missing events in Outlook (in different views), I noticed that some of the events were missing their start date.  I tried manually editing them, and it worked for a couple appointments (they showed on the calendar afterward) but most of them say, "Can't open this item. The end date you entered occurs before the start date."  (On my own calendar, when I tried deleting the old appointments that were missing their start date, I got an error saying it couldn't properly delete the items, and if they were scheduled with other people, they might not receive the update.

I've read several solutions on this or similar issues, including Outlook /cleanviews, Outlook /resetfolders, Outlook /cleanreminders, Outlook /cleanprofile, Outlook /cleanfreebusy.  I tried the first three on my machine, but it didn't fix what they said it would.

I have the MFCMAPI tool, which some said helps, but some said deleted their future appointments, so I tried it on my own mailbox, but I'm wary of deleting items from their mailboxes; they're our Sales Team, and if they are missing appointments with customers, that would be a big deal.

I read clearing frmcache would help, as well as opening the Calendar properties and clearing the offline folder, as this will force a resync of the mailbox and offline calendar.  (I tried the latter on my own calendar, and it cleared it all right, but it did not sync properly afterward.)

We're running Exchange 2003 Enterprise SP2 with Outlook Pro 2003 clients on Windows XP SP2.  I read this can also be caused by file-level AV, but the only AV running on the server is Trend Micro ScanMail, and I have the only scheduled scan disabled.

I'm so frustrated.  This is all I've worked on today, and I don't think I've gotten any closer to a solution.  I wish I had thought to post sooner.

Thanks in advance for any input or suggestions.