Freezing after overheat/start-up freezing... major issues

Question

Hi guys,
Quick back-story is that my G5 runs my Pro Tools HD system. I left the control room for a while and forgot to turn the AC on. Yep, stupid. The room got very hot, but keep in mind... I have NO idea if this was part of the problem or just coincidence. I came back and the machine was frozen on the display-saver. I forced down, restarted and it's never been the same. I've tried every trick I know... resetting PRAM, verifying disk permissions, starting without extensions and I even tried to reinstall OSX, but it even freezes from the startup disk. It says the memory is O.K. in About this Mac.
So, I booted from the CD to see if I could do a verify disk from the CD, and it just freezes a couple minutes in every time. Every once in a while, I'll get it to start up properly.... then I'll launch a few programs and it just cold freezes after a few minutes. It's not a kernel panic or a spinning wheel... just a hard freeze.... mouse stops working, you know the drill.
So, I'm somewhat fearful that the issue here is hardware-related. I'm trying to continue to do an Apple Hardware test from the CD, but freeze-city.
I can generally sort my way though this kind of thing. I've had gobs of these over the years, but this seems different in the way it's behaving.
Yes, I can take it to a shop. Just wondering if anyone has any speculation or ideas I may have missed.
(More back-story, I run Pro Tools HD on the PXI-X cards, so I have to have a G5... Mac Pro won't work for me, so I could buy another used G5 if I had to, but it's the set-up that's the nightmare.)
Thanks for any help!

Answer 1

Hi WCR-
I'm somewhat in the same boat. If you see my threat (G5 2.0 DP June 2004 Won't Boot!) I am experiencing similar symptoms. I've replaced every component in my box except the power supply and both processors - and everything I experience leads me to believe the problem is a blown processor, the "1" position. Now my machine won't even see CPU1 - just CPU 0. If you can keep it alive long enough, download the disk image for Apple Service Diagnostic from apple.com and see if you can run diagnostic tests on the CPU's alone. That will at least answer that question.
Unlike your situation, I got the computer in a broken state, so I don't know if heat is what caused the issue.
I guess that doesn't really answer your question, but at least don't go dropping a boat load of money on a new logic board, because it hasn't fixed my problems - it probably won't fix yours either.