Have you see this error yet? If you haven’t, you will. This is one of the most common errors and can be seen while performing a variety of functions within Exchange 2010. I continue to see this issue pop up so I decided to write a post on it. Most recently I saw this while trying to attach a disconnected mailbox to an existing AD user account. I have seen this same error pop up during the following functions (not full list):

Reconnect mailbox
Move mailbox to another database
Enable user for Unified Messaging
Creating an Outlook profile

Continue reading at this link. Tanks Tim Harrington.