Trouble with iPod freezing, etc

Hi, I have a 40GB iPod (it's a year and a half old, thus long out of warranty), and while it frequently freezes, it's easily reset. However, recently it freezes, can't be reset, shows the sad iPod icon, but can be operational again after being set in disk mode. Today, it froze, sad iPod icon'd, and after being plugged in to my computer alternately displays: sad iPod, the still "battery charged to one bar" icon, and the apple icon. When I try to reset it while plugged in, it repeats this cycle, and when I try to put it into disk mode, the screen goes blank and stays like this for as long as I hold down the center and play buttons. If anyone can help after reading this long description, you would be my hero/heroine. Thanks.