I have inherited a client with NT4 and Exchange 5.5, and some issues. Specifically, several of the users can not open some folders in their mailbox, but can open others. For instance, one user can not open the Inbox in their mailbox with Outlook, but can open other folders in the same mailbox. The Outlook gives the grey screen with the error "Unable to Open Inbox". Another user has the same issue with the Deleted Items folder. I checked the permissions through Oulook and they seemed correct.
What is the best way to debug this issue?