The process cannot access the file because it is being used by another process.

Hi. I'm using BE 9.1 4691 together with a NAS - Buffalo LinkStation. I run two backups per night. First to the NAS and then a Duplicate job that takes this backup and shoves it to tape.  The above error is becoming more common so hence this question.  This error occurs on the startup of the Duplicate job and I can only conclude it is referring to the backup file recently created. What can possibly be using the first backup file on the NAS other than BE itself?  Can I add a delay factor between the two jobs? It looks like the first job does not release its hold before the Duplicate starts up.  I also happen to know that using Windows logons to the NAS (linux OS, I think) causes all sorts of problems if you log on twice from the same machine.  Pointers most welcome.  Thanks in advance.