This is a known issue with mailboxes previously migrated to Exchange Server 2007 using Quest Migration Manager (QMM) version 8.5. According to the Quest support site, this is resolved in the next release of QMM, version 8.6.
The resolution can be found at the Quest support site:
Mailbox move from Exchange 2007 to Exchange 2010 fails with error "Unable to synchronize manifest"
Note: You may need to either logon or register on the Quest site to access this information.
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.