The question I would first ask is what sort of problem are you having with this user's mailbox?
It would be worth checking out this Technote as it may help you with re-associating the mbx to the archive.
How to migrate users from one Exchange server to another
We use HTC smartphones with Android. One of our users are having problem when synchronizing the calendar, it fails with a timeout error. Have tried on the same phone with my credentials and it works perfectly.
So I was thinking about exporting the users mailbox, deleting it, re-create it and then import the mailbox.