PB puts itself to sleep when in use

Question

The powerbook will put itslef to sleep with no warning. I will be working as normal on my computer and all of a sudden the computer diplay will go black, and the sleep light will begin to blink. I am not certain if the hardrive also goes to sleep, but im pretty sure it does. Sometimes it will happen as soon as I rewake it, and in most cases this ends in the computer freezing and forcing me to remove the battery and AC adapter to simply restart it.
I have tried reseting the power management unit, removing external devices, and instructing the computer to not sleep at all. It seems to happen at random, for instance, atm, it seems to be working fine, but it could go to sleep at any second.

Answer 1

I have had the worst time with my PB for about a month now. It all began when my hard drive crashed. I Replaced the HD.
Reloaded and updated the OS and all software.
Then, after about a week of everything running like it should, I began to have problems brought on by encrypting my data. My PB began to freeze. I spent about - and I'm not exaggerating - 3 1/2 hours on the phone with Apple Care. Finally had to zero out my hard drive and - once again - reload EVERYTHING.
Everthing was fine for about a week and then, out of the blue, my PB would go into sleep mode - while I was typing.
I spent another 2 hours on the phone with Apple Care. Finally had to zero out my hard drive and reload everything - AGAIN!!!!!!!!
Imagine the frustration when - after I reloaded everything which takes at least 3-4 hours (after downloading upgrades and all) within 15 minutes it went back into sleep mode while I was typing!!!
At this point I was just about ready to throw it out the window.
Instead, I brought it to the Genius Bar.
They took it in and replaced the mother board (the error log stated something about a printer error though it wasn't on line with the printer).
I got the PB back the next morning and began to check my email when - guess what happens - yep, it went to sleep while I was typing!!!
Each time it went to sleep I was able to wake it up after about 10 seconds by pressing a key. It would stay on for about 7 - 10 seconds before it would die again. After going through this cycle about 10 times it wouldn't wake up until I removed the battery. When I turned it on this last time I went immediately to the error log to see what was happening and this time it said "excessive temperature".
Okay, so I went back to the Genius bar (amazingly, no blood was shed), and this time they sent it somewhere to be fixed.
I'm waiting for it to come back. Though with all the problems I've been having with it I'm actually quite afraid of getting it back and having this or something else happen.
I've got to say - through all this - the only reason I'm still sane is that everyone that has assisted me, whether on the phone with Apple Care or at the Genius Bar, has been absolutely fantastic! I love those guys! And, I love my PowerBook - I just want it back - the way it was - before all this started happening!
I've been doing a lot of searching regarding this problem and - although Apple techs seem to have never heard of this problem before(???) - it has been happening to A LOT of people that have PowerBook G4's 15" and 17" built during 2005. It has to do with the TrackPad Sensor going haywire and the Topcase must be replaced - perhaps the motherboard as well.
If you speak with an AppleCare tech tell him to read this: http://communitymx.com/search.cfm?searchtype=Basic&searchbox=PowerBook+Sleep&sub mit2=Search&shortLong=1&searchinside=0
GOOD LUCK!