Outlook pst files are locked by DLO

Hello,

A customer has problems with his users. They make in the profiles that all files of pst must be backuped, the problem is when the users try to open outlook, because the pop window appears saying that there is another application that using the pst files, then the outlook is closed.

Of course, the other application BE DLO.

Are there any that knows how to solve this?

Carlos Espinoza