Need some troubleshooting advice. I bought a new Sony Walkman today and charged it for 3-4 hours (connected its USB cord to my computer - yes the PC was powered on). The Walkman will turn on but won't stay on more than 4-5 seconds. Its display reads that it is fully charged. A small lighted message ("HOLD") illuminates and blinks at the top of the screen. I can't navigate to any the menus and it shuts off after a few seconds. Can't find any help in the manual for any of this.