How did you migrate the mailboxes from the Exchange 2003 to 2007 ?
I think unless you used the tools on the exchange server to move the mailbox, the blackberry related information is lost.
But, you say, you cannot activate a new user ?
have you tried to create a new empty mailbox + user account, and then activated this without success ?
Have you tried to use iemstest.exe (in the utility folder of the BES program folder) on a user ?
there is a KB article: http://btsc.webapps.blackberry.com/b...rnalId=KB13842
dont know, if that matches you problem, because there should me more on the log then just user xyz not started.