I think i had the same problem, the model i posess is the 40gb, one of the earlier models 2 years old iirc.
I had the 'complaint' delivered to me in the form of the sad looking ipod icon and then it just cut out. After much deliberation with forking out £70 to get it fixed i just abondoned all prospects and left it to collect dust.
However, my sister managed to revive it some months afterward by simply pressing the 'play' button on the fly wheel and then sharply hitting the top righ-hand corner of it with the palm of her right hand. Somehow this 'jogged' the HD into life (as previously whirred a little then cut out repeatedly for about 1 minute). Problem solved! my iPod has work relentlessly to this day! I would, however exercise caution when doing this, even if it does work, the inevitable long term damage is yet to prevail.
Kind of a candid approach but it worked for me