Sounds like their fancy way of saying that the hidden message that contains
the out of office settings is corrupt. Two ways to address...
1) Export the contents of the Exchange mailbox. Delete existing mailbox and
create a new one for the user.
or
2) Use a tool like OutlookSpy (
http://www.dimastr.com/outspy/) and delete
it. (I was hoping there was a screenshot of the interface that I could
point you @, but one isn't posted on the site.)