This issue would happen when you download a file from Internet or Network Location, etc. Windows now preserves the zone information for file(s). This identifies where the file came from and displays appropriate warning messages, indicating you to be careful.
Resolution: Go to the properties of precompiled dll’s, check to see if it has following security message (at the bottom of the window): "This file came from another computer and might be blocked to help protect this computer." If present, click "Unblock", "Apply" and "OK".
Details, refer here: MSDN Blogs: System.Security.SecurityException: Request for the permission of type