On a Windows XP system that was in a domain using a Microsoft Exchange server, whenever a user attempted to use Outlook 2003, Outlook would start to open then crash. The error message displayed was "the set of folders could not be opened." I confirmed that the user's Outlook .ost file still existed and that the user had appropriate access permissions. I also ran the
scanostutility that Microsoft provides with Office to verify the integrity of the user's OST file. It did not find any problems with the file. I found the problem was on the Exchange server. The mail store was not loaded due to inconsistencies in it after a system crash. When I repaired the mail store and the Exchange server was running properly again, the user was able to open Outlook normally.
I don't know why this problem only occurred on this user's system. Outlook 2003 opened normally on other users' systems. They were not able to access email on the Exchange server and Outlook indicated they were disconnected from the Exchange server, but they were at least able to access email, contacts, etc. that were stored in their OST offline storage files.
Repair an .ost or .pst file in Outlook
Office Online Home Page
Repairing Outlook PST File Corruption at 2 GB Limit
Using ScanOST to Repair OST Files