You can get around the hang-up by
selecting all the files you want to move and dragging them ONTO the
icon of the destination folder on your Gnex (i.e. don't open the
window for the destination folder and drag to that, just drag them
onto the folder icon itself).
Yes! Perfect fix. Don't install drivers, don't root phone, don't enable USB debugging, just drag to folder icon (tested pn Win 7)