I made a bootable usb stick and used it for a while. I then messed with one of the .lzm files in the "base" directory. I don't think that would have messed up anything but... Now my usb stick is apparently a read-only filesystem. I can't delete or put anything on it, even as root. What could I have done to cause this? Or is it a defective usb stick? Would reformatting it help?