Exchange 2003 Mailbox Store missing (private information store)

2 days ago our exchange server fell over and reebooted itself. We're still looking into why it fell over but that isn't the main issue.

After rebooting it hung at "applying computer settings" and we discovered that the service "Microsoft Exchange Information Store" was hanging in a "starting" mode.

We eventually tracked down that this was because the group "Exchange Domain Servers" had been moved from the "users" container so we moved it back and rebooted.

Since then the mail has been working again. Everyone can send and receive sucessfully. The problem is that the Mailbox store "Personal Information Store" has gone missing and is no longer residing under the "first storage group" where you would normally expect it to be.

This means that we get a "c0072030 Microsoft Active Directory - Exchange Extension" error when trying to change mailbox rights and also we cannot create any new mailboxes.

Any help with this problem gratefully received.

Thanks,
Karl