DJ Pixel Juice

I've had a few of the memory stick type of sony walkmans and never had a problem with them until now. I've had the NW-S706F one for over a year and it's worked great until two days ago it went from having a full battery to randomly quitting on me. The strange thing is that it would start working again after a couple hours. Well, today the volume up button no longer lets me control the volume, and the volume down button only turns the volume up. The seek down button has no function. I've tried reformatting the device from the menu, but this doesn't fix the problem. The reset button also has no function. If anyone has any ideas or suggestions I'd greatly appreciate it.