Powerbook G4 won't boot (sort of)

[disconap]

Ok, so I have a very unique, bizarre problem. A friend brought her G4 1.67gHz 15" Powerbook to the office to have it looked at as it wasn't working properly. I took a look at it and found that one of the RAM chips was shorted out. I took it out and ordered her a new pair (since it was like $26 for 2gb, and with the one removed she was running on 512).

Here's where it gets bizarre: I installed the new RAM and it was freezing regularly. I then took one out and it was still freezing regularly. I booted it from my Utilities partition (I have a bootable firewire drive set up to fix problems and recover data) and ran Disk Warrior, TechTool, and a whole heapin helpin of other fixin and optimization apps. I got it to fix all the reported errors, TechTool reports no hardware errors, everything should work perfectly.

So now, the laptop boots to a blue screen. I can't boot it from a retail Tiger install disc, and I can't boot it from the hard drive, it just boots to the Apple logo, the Unix spinner, and then goes blue and freezes.

So I set it as a firewire target drive and was able to do an archive/install of Tiger using my G5. It recognized and installed fine and it booted my G5. Ok, so it's not the drive. I restart and nothing, apple/unix logos then blue screen. Same with the Tiger DVD. I replace the original 512MB stick (the working one) and still same result. So finally I go back to my Firewire repairs disc and everything boots fine, all tests come out fine, drive is recognized and works fine, etc.

So any ideas? What could cause a computer to boot, a drive to be bootable, but a computer not being able to boot on any installed drive? I'm honestly baffled at this point...

 

[SHADO]

Have you tried a PRAM and VRAM reset? That is very weird though lol.

 

[disconap]

Yeah, I gave that a shot as well. I eventually cleaned up the drive as best I could and returned it to her with the advice "you should take this to the Apple store and have the genius bar run some diagnostics on it", since the only thing I couldn't run was the Apple Hardware Test, since I didn't have the specific disc and the one I burned from the Apple support page wouldn't boot. *shrug*

I'll post back with the result if they come up with one. I personally think that either the thermometer isn't telling the fan when to kick in (so the freezes are the system overheat prevention dealy) or that something in either the RAM bus, drive bus (since the PBG4 had a shared bus for the HDD and optical drive), or processor itself is wonky...