Itunes Stopped Access Not Permission

My iTunes has suddenly stopped giving me access giving the message "The iTunes library .itl file is locked, on a locked disk, or you do not have write permission for this file." The iTunes forum says that I need I need to uncheck the "read-only" attributes by right-clicking on the iTunes folder, select properties, unselect Read-only. So I did and received the message, "You will need to provide administrator permission to change these attributes, click continue or cancel. I clicked continue. It ran "applying attributes" and then I clicked ok. But iTunes still gives me the same message that the file is locked. And then when I back into properties the read-only selected again.