AutoCAD 2010 :: Modifying Drawings - Read And Write Privileges

There seems to be a glitch in AutoCAD with allowing another user to access a drawing that someone already has open. Most of the time , it will not allow this and will correctly give the message that someone is already in the file and give the option of opening file as read only.

There have been a few times though that someone will not be prevented from accessing the file and the read and write privileges will be transferred to the new user that opened the file last. How do we prevent this from happening??