I got a MD walkman Mz-nh600 and after a while the buttons have started to play up and are not working proply like the menu button wont work at all and the jog control won't work either. The only buttons that work are the play and stop button But while it will play the (cannot edit) message comes up and the sound cannot be changed usless i hold it up or down. If anyone can help that would be very handy there is also SU on the screen that hasn't been there before and i've lost my manual so what dose that mean Josh