IBook puts itself to sleep and/or shuts down

Question

My gf's iBook G4 (14-inch Early 2004) puts itself to sleep at random. No amount of pressing keys will wake it up, only pressing and holding the power button to shut it off completely, then rebooting, will get it back. Sometimes it shuts itself off completely at random. When starting it back up, it often refuses to boot all the way: will start to display the grey screen, then turn itself off. Resetting the PMU seemed to help for about an hour, then the same problems started again and now I can't get it to boot up at all. It won't even boot up into target disk mode so I can rescue her data with my Powerbook, nor will it boot from CD! Resetting the PRAM had no effect. She's understandably quite upset and thinking of getting a new computer. Is there any less expensive fix for this? Any help would be greatly appreciated.
Thank you.
[edit]
By the way, I've read the other threads here describing similar difficulties, but I doubt the problem is the GPU needing to be reballed. The machine won't start up at all, rather than being started but having a black screen.
[Additional info:] I had noticed during it's last successful boot that the battery was dead in spite of the power cord having been plugged in to a working socket for days (and yes I'm sure the socket works). I've also tried with the power cord for my Powerbook with no success, and verified that her power cord works by plugging it into my Powerbook. This is what lead me to try resetting the PMU, but as I said that didn't work. Could it be that the PMU itself needs out-right replacing? If that's possible, is it possible to do so without replacing the entire logic board?

Answer 1

Joel,
I don't think leaving it on all the time was much of a factor other than wearing the battery down faster which, according to Apple, has a approximately a 1-2 year life. Mine went before the 2 years was up and it's $129 to replace it.
Using it with the battery while it's plugged in without air circulation or a laptop cooler might be some extra wear and tear. Mine runs the hottest during that time, but if I unplug it and just use the battery, it cools way down. I'm interested in which iBook your GF has because a friend out of town has been reporting the same problem and I figured she didn't know it was sleeping. Hers is a 14" 1.0ghz I believe.
The case is supposed to be really strong, made out of bullet proof material, so the Apple sales rep told me, and it can survive an accidental minimal drop, unlike the PBs. I haven't tested that, but another friend dropped her 12" the other day, while it was open, and it looks like it just loosened the video cable. I haven't opened it yet to find out.
Is there any chance that the energy control panel was turning it off? Mine turns on EVERY morning at 3:10am even though I have unchecked the box for it to do that. It came that way from Apple and I thought it was so it could run the maintenance tools. I have no idea why it still turns on, but it's not a (future) problem that I know of.