PowerPC :: Unable To Boot G4 From Retail Tiger Install Disc

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. What could cause a computer to boot, a drive to be bootable, but a computer not being able to boot on any installed drive?