When transitioning from Exchange 2003 to Exchange 2007, one of the steps that you would have to perform is a Mailbox move from a legacy system to the new system. In my case, the error I kept on getting was that the address list service wasn’t running or that the email policy was faulty. Depending on your error there are different fixes for this, but in my case I had a Mailbox Manager Settings Policy (Journaling) configured on my Exchange 2003 server that was preventing the mailbox move process. This blog helped:

http://telnetport25.wordpress.com/2008/03/30/quick-tip-upgrading-the-default-email-address-policy/