Question : Migrating Mailboxes

Receiving the following error when trying to migrate mailboxes from Exchange 2000:
Error occurred in the step: Preparing
mailbox to be moved. Failed to copy basic mailbox information with error: The
Microsoft Exchange Information Store service could not find the specified
object., error code: -1056749241

Checked and changed permissions on the mailbox store, tried several mailboxes.
Thanks,
Bill

Answer : Migrating Mailboxes

Your permissions are all banged up.

See  http://support.microsoft.com/kb/938444

Specifically

Additionally, if you move the mailbox from Exchange Server 2003 to Exchange Server 2007, you receive the following error message:
-1056749241
This issue occurs after you successfully install Exchange Server 2007 with the following roles:" Hub Transport  
" Client Access Server  
" Mailbox
Additionally, you can successfully create new mailboxes in Exchange Server 2007.
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CAUSE
This issue occurs if Read permissions were removed for the Authenticated Users group in an organizational unit.

When this occurs, Exchange Server 2003 continues to authenticate clients. However, in Exchange Server 2007, the Exchange Servers group is a member of the Authenticated Users group, and this group is missing the Read permissions for address lists. Exchange Server 2007 uses the ShowInAddressBook attribute to authenticate clients.
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RESOLUTION
To resolve this issue, grant Read permissions to the Authenticated Users group in the organizational unit where the user account is located.

Note In special hosting environments, you may not be able or willing to grant authenticated users Read permissions. In this scenario, you can grant Read permissions to the Exchange Servers group in the organizational unit.