Power Mac G5 PPC Screen Freeze Turbo Fan Issue

Question

Hello...
I've read most, if not all of the related posts; however, I have not seen any definitive answer to this issue.
My, almost mint condition, Power Mac G5 PPC has recently started the screen freeze, turbo fan, won't boot issue that seems to be prevalent with these models.  I've tried almost all of the suggested troubleshooting fixes and have had no luck.  My most recent attempt was to try and start in single-user mode (holding SHIFT + S at startup) and I received the following error screen then turbo fans: http://www.thishateofmine.com/Assets/photos/appleCPUpower.jpg
Remember...this is a PPC, so why am I getting an error referencing Intel CPU Power Management?  This leads me to believe the OSX 10.5.8 I've been running has installed system resources for non-existent CPU's and is causing a conflict.  This would be a major coding error on Apple's behalf, would it not?
I never had this issue when running any previous OS version and this computer had been running spectacularly.
It has only been used in my clean, smoke-free, home recording studio and if it werent' for a few blemishes left by external HDD's, this computer could pass as brand new.  There is very little internal dust and I have kept it clean with electronics approved compressed air.  I have not removed anything to get at the PSU area for cleaning, though.
If I could get it to boot from the original DVD's and install up from Panther, I would.  Based on the error message I'm receiving, I do not believe this is a logic board, RAM, CPU, etc... issue.  The computer will boot into open firmware and function fine, but not the OS; therefore, this would be an OS problem, right?  Is that not a logical mental path?
This HAS to be a known issue and have a resolve that is NOT logic board and/or CPU replacement related.
Any help would be greatly appreciated.
BTW...please read this as a positive communication from a frustrated (knowledgeable enough to be dangerous) user.  I just want my G5 back. 

Answer 1

After plugging in the G5 PPC, as it had been unplugged for several days, here are last night’s efforts:
With only the original, main Hitachi Deckstar 400GB HDD in slot 1, I attempted to boot normal, boot holding SHIFT + COMMAND + V, boot holding COMMAND + S and boot to the original install DVD, all with no joy.  In my original post I incorrectly stated I was attempting to boot into single-user mode by holding SHIFT + S, which resulted in the screen displaying the OP’s linked image.  In attempting to boot into (actual) single-user mode and verbose mode, I get two different text messages – and have taken screen photos, but have not been able to upload yet – both of which stop with “DART enabled” and then do nothing else with no cursor capability, only to result in turbo fans and having to hold the power button down to shut down.
Next I ran (again) the Apple Hardware Test from the original install DVD and everything passed. 
Feeling confident the hardware is all in working order, I used my brother’s Macbook Pro 3.1 (OS v10.6.8) as the host to mount the G5 PPC in target disk mode.  The PPC’s HDD mounts up with no issues and everything is accessible, so I shut down and swapped the original HDD with a 500GB Western Digital Caviar SE16 that did not have an OS on it, restarted to AHT DVD and ran test again with everything passing.
Now I reconnected the target disk mode setup, formatted the PPC’s WD HDD and installed Leopard on it while in TDM from the MBP3.1.  Everything installed, restarted will still TDM connected, MBP3.1 started up with the PPC’s HDD as the startup disk, went through all the typical initial install information and registration and voila I’m back in target disk mode with the PPC’s HDD as my boot disk and MBP3.1’s HDD on the desktop.  Everything’s accessible, functions and looks good.
Keeping in mind I’m only dangerously knowledgeable regarding computers, I’m thinking I should be able to shut everything down and now boot the G5 PPC from the internal WD HDD I just installed the OS on, right?  Wrong.  All I get is the infamous folder with a flashing question mark.
Help!!!  (…please???)
BTW…as it has been mentioned in a few posts, but is one thing I have not done yet, I thought it worth mentioning.  I have not replaced the internal battery, but the last time I was able to get the computer to boot to the internal HDD and run for a short period of time, after being unplugged for several days, I did have to re-enter time, date, location, etc… info.  The actual last time I got it to boot, I did not do this, as it only got as far as loading the desktop before freezing, but the time was correct.  Didn’t get a chance to check date and location, as it froze almost instantaneously.