Errors when backing up using BackupExec

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What causes this?
How do I get rid of the error??

Access denied to file Andrew Smith [andrew]?Top of Information
Store?Calendar?n.
The item \\SERVER-EG\Microsoft Exchange Mailboxes\Andrew Smith [andrew]?Top
of Information
Store?Calendar????????????????????????????????????????????????????????????????????????n
in use - skipped.
V-79-57344-33928 - Access is denied.


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