I've copied MP3s onto my Lumia 930 phone with no problems so far. Today, for no apparent reason, when I try to copy an MP3 (one of my own pieces of music) onto the phone, I'm getting a message saying "You do not have permission to create this item". The folder I'm trying to copy into is in Music/My name/Album name. There's nothing special about this folder as far as I can tell. Has anyone any idea as to what could have caused this, please?