Cannot Move Mailbox from Exchange 2003 to Exchange 2007

Question

Hello,
     I am migrating exchange 2003 to Exchange 2007 and have moved almost all the mailboxes without any issue, but there are some mailboxes which are not being moved since they are giving me the below error.
Error:
Error was found for John Doe ([email protected]) because: Error occurred in the step: Opening source mailbox. Failed to open mailbox with error: ClassFactory cannot supply requested class, error code: -1056749262
Initially I found that the account was disabled from Active
Directory so enabled it but and also replicated the active Directory but still the problem is there, its not hidden in the GAL aswell.
http://www.arabitpro.com

Answer 1

Thanks everybody .. I have solved the problem myself. 
To resolve this issue I had to give the account "SELF" permissions for "Associated external account". If the user does not have these
permissions to its own account it is unable to set the msExchMasterAccountSID attribute for the disabled account causing the error. By setting this permission on the disabled account, it allows it to mark the msExchMasterAccountSID attribute.
To do this follow this procedure:
1. In the Active Directory Users and Computers snap-in, on the View menu, click Advanced Features.
2. In the Exchange Advanced properties of the disabled user object that owns the mailbox, click Mailbox Rights, and then search the list of accounts for one
that has the Associated External Account permission.
4. If no account has this permission, grant the SELF account Associated External Account and Full Mailbox Access permissions.
https://support.microsoft.com/kb/278966?wa=wsignin1.0
http://www.arabitpro.com