Within the last couple of weeks we have experienced some odd calendar
problems with the workstation version of Outlook.  Here are the symptoms:
•    When you make or accept an appointment in Outlook WebAccess (OWA) or on a
PDA phone, the event does not synchronize properly to your workstation
version of Outlook.  In fact, it will not show up on your Outlook calendar.  
It will show up on your OWA and PDA phone calendars.  If you search for it in
Outlook, you will find it, but then when you open the appointment, it shows
today’s date.
•    When you receive a calendar invitation in Outlook and open it, it looks
fine, but if you click on the Calendar button within the event to see what
else you have going that day, you are taken to August 31, 4500 (the last day
you can schedule anything in Outlook).  If you accept the appointment,
however, it goes to the correct date and time in your calendar.

We run Exchange 2003 with the latest service pack.  The problem is happening
on both Outlook 2007 and Outlook 2003 all running in Cached Exchange Mode.  
Computers are Windows XP.

For troubleshooting we have:
1.  Done a Detect and Repair in Office
2.  Created new profile for the users
3.  Deleted the OST file and recreated it
4.  Uninstalled that last 2 Office Outlook 2007 fixes from Microsoft

Anybody got an idea of what to try next