On the side of a SD card there is little groove/notch with a small plastic slider in it. That slider needs to be in the closest position it can be in the direction of the reader pins. [http://www.youtube.com/watch?v=58pdnjskvyw&feature=related|Here is a video] sowing you how to unlock the SD card. [http://www.youtube.com/watch?v=xhaoEWuy8XA|Here is a video] showing you how to fix this problem if the little slider is broke or missing.