I have heard about this a couple of times now… Here is the only docs I have really found on it
Which contains
After some work, we were able to determine why Outlook 2003 crashes after
moving mailboxes off of Exchange 2000 onto Exchange 2003.The fix is to add a registry value “Guid-Replid Caching” under
HKLM\System\CurrentControlSet\Services\MSExchangeIS\\\Under each mailbox store we added a reg-dword “Guid-Replid Caching” with a
value of 0.
Wow this is big for us where I am. What kind of things are you hearing Joe? Does Outlook crash once or does it continually crash until this value is added?
We are preparing to move thousands of mailboxes off Exchange 2000 to Exchange 2003. I’ll let you know if we encounter any of these issues.
To fix the Outlook crashing, you will need to restart the IS. To prevent future mailboxes being moved from having the problem, you need the reg change and then restart the IS.
It doesn’t just cause Outlook crashes. It can also break delegates as well as free/busy.