I have heard about this a couple of times now… Here is the only docs I have really found on it
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
Under each mailbox store we added a reg-dword “Guid-Replid Caching” with a
value of 0.