why does my ipod slow down playback?

I have a 3rd Gen iPod Classic which has worked flawlessly until just recently. It has started to play back my mp3 files at a slightly slower tempo but enough that it is really disconcerting. Does this mean that the unit is dying? Like maybe the hard drive is on its way out? I know newer versions have a speed control. Not mine. Has anyone out there had a similar experience? Any help here would be greatly appreciated.