Ahh man, mine did the same thing...4G 20gb. Broken screen, spazzed out on me while updating. I threw mine (quite literally threw, rough day..) in my closet and forgot about it for a few weeks, when I picked it up again it worked, I loaded about 300 songs to it in haste before leaving the house, when I tried to load more it died again and has never recovered.
When you press a button, does the hard drive spool up, but not do anything? Just kind of keeps spinning for an abnormally long time? I just got a 5g 30GB today to replace it...I'm considering grabbing a cheap external enclosure to put the hd in, then I'll know if the disk died or if it was the firmware that fried instead..