SO, I plugged it into a windows machine, ran 'diskpart', 'select disk 1' (or 'list disk' to be sure the disk number!), then 'attributes disk clear readonly' (and 'exit'), but nope, still a read only disk (whether using windows or mac) Me too (using a 16GB usb stick) I could write to it for a couple months (nothing excessive), but then today is went mysteriously to read-only