Blue Screen of Death - Help!

[alphanumeric]

I've read previous help topics about the fated blue screen of death, but this one is a bit different, and may require a different solution/approach.

After two years of use, my G4 IBook now freezes at the blue screen of death (just past the apple logo/progress indicator).

Machine paramaters are basic. G4/1ghz/256mb ram/40gb/14.1. Running 10.4.7 and the only periphereal is an airport extreme card.

Things I have tried already:

1. Disk Utility
2. Archive and restore.
3. Apple help site steps (http://docs.info.apple.com/article.html?artnum=106464#symp1)
4. PRAM (included in above) multiple times
5. Fireware update and reset
6. Resetting airport card (I was getting desparate for a solution)

The good news:
1. It now starts in Safe Mode reliably (it didn't before)
2. It will enter target disk mode
3. If I use the firewere target disk mode to set my iBook to the startup disk for my iMac, no problems occur... I can see and boot from the iBook through the iMac.

The bad news (and odd things):
1. When cold (no power for 2 or more hours) the iBook powers and functions normally, but then quickly freezes within five minutes of use. And on restart returns to the "blue screen of death" problem.
2. Switching my iMac to target disk mode and directing my iBook to boot from that disk results in the same blue screen of death problem. This would leads me to believe that there is hardware problem, but would that make sense if the freeze happens in the same place?

I am now in the process of backing up everything to a storage drive in preparation of a total wipe and reinstall, but my storage drive is USB so it will take me a few hours to do this.

However, I'm not at all confident this will fix my problem. Any help or ideas you may have are greatly appreciated.