Did you check the battery cable? Unplug it and plug it back up. If that doesnt work i would probably give in and have it serviced. It could be a solder joint or it could be that a part got broken. There are no service manuals available for it so if it isnt something obvious it wont do you any good getting it open.

On a side note.. theres one on ebay for $120 right now. Keep an eye out there and you might find a used one for less.

I am in a similar situation with a laptop. They want $200 to repair the power connector but i can find the whole laptop on ebay for $200 so i cant justify the repair and i really dont need a Pentium4 laptop so i cant justify the ebay purchase :).