Exchange backups may fail with:
Unable to complete the operation for the selected resource using the specified options. The following error was returned when opening the Exchange Database file: ' n/a '
This issue has been observerd in Backup Exec 2010 R2 even after Hotfix 143746 has been applied and in Backup Exec 2010 R3, this issue has been observed to be intermittent and at random.
0xe00002f7 - Cannot extract mailbox messages from the Exchange backup. Review the job log for more information.
This issue has been resolved in Backup Exec 2010 R3 Service Pack 2