Backup Exec 2012, Exchange 2007, GRT restore

Hi All,

I'm attemping to restore a mailbo with GRT from Backup Exec 2012 from a Exchange 2007 backup.

I've got my media library updated with the newest magement tools and the server has the matching level of updates.  I've run the Symantec Help tool on both the mdeia library and the Exchange server, and they've reported no errors.

My steps to restore are;

I've recovery groups made for the storagegroup I'm restoring. Their databases are dismounted.

From within Backp Exec, I've selected Exchange Server, Restore, Select Microsoft Exchange, Microsoft Exchange Mailbox Items, selected appripoate date, then restored to another location, which I've specified as 'computername', then as a PST to c:\temp

The job runs for 30 minutes and then I get the error 

Job ended: Monday, 10 August 2015 at 3:10:53 PM
Completed status: Failed
Final error: 0xe0000395 - Cannot extract mailbox messages from the Exchange backup. Review the job log for more information.
Final error category: Resource Errors

For additional information regarding this error refer to link V-79-57344-917

Errors 
Click an error below to locate it in the job log
RestoreV-79-57344-917 - Unable to complete the operation.  The following error was returned when opening the Exchange Database file:  '-1032 The file cannot be accessed because the file is locked or in use. '

I've researched that error and all I've come up with relates to doing backups, not restores.

I must be missing a step, can someone assist in poinitng me in the right direction?

Thanks