Dual 2.0 G5 Failed today- Anyone have ideas on this?

Question

So today my G5 worked great, as always. Running multiple apps, running fast, blasting through my work. Nothing unusual. Then Photoshop decided not to open a file. So, I force quit, went to re-open, but the dock icon would just bounce once. After a restart, this wasn't fixed. I went to Safari to look for some troubleshooting pages, but got an unusual web error about the server not existing (I believe), rather than the usual "You aren't connected to the internet do you want to run network diagnostics" message. I opened the system prefs and the icon for the network was gone?! After poking around a little more, the system froze, giving the restart screen. Rebooted, same thing, froze after being on for a few minutes. I zapped the p-ram, ran disk utilities, hardware test.
That's how it started, and here are the computers major symptoms (other than what was already mentioned, as none of them were was fixed):
->won't mount any of the external drives (one is usb, one is firewire)
->won't mount any cds (but will boot from one)
->there is no option to look at the hardware, network or devices in the system profiler
->no applications will launch, except apple ones
->no network/internet
->the desktop pictures are set to change every few minutes, and no longer nicely segue! Just jump to the next picture (minor problem, but weird)
->hard drive mounts fine, everything appears to work until you actually try to use the computer!
Test Results:
->hardware test (version 2.1) said the logic board's backside fan has failed (but I've read this result comes up and is very often faulty on the G5s, and that the hardware test is bs and unreliable)
->disk utilities found some errors, but fixed them, with the exception of a few "overlapped extent allocation" errors
->computer has had the problem where it won't boot and the fans sound like they're going to spin out of control (this was never fixed, just kind of came and went and we shut the computer down less often)
Computer stats:
Dual 2.0 gHz G5 (the first model from late '03)
4 GB RAM (2 GB are from OWC)
OS 10.3.9
I did not re-install the operating system. The computer is already in the shop, but there's a 5 day wait before it can even be looked at. In the mean time, I wanted to ask around and see what may cause this and if I could fix it myself (I can go back and get it!). I also would like to know more so I can discuss it with the techs if necessary. It seems like a hardware problem, considering how it worked fine, then didn't. What I've found online points to the logic board being faulty? Or, perhaps a failed processor or a conflict with the aftermarket RAM? Could re-installing the OS have a chance of fixing this?
Thanks in advance!!!
Selena
Dual 2.0 gHz G5 (late '03)   Mac OS X (10.3.9)  
Powerbook G4    

Answer 1

It really sounds like a hardware problem. This is a shot in the dark (but what isn't at this point?) but something like this happened to my iBook (of course while I was traveling) -- it had a similar array of bizarre and seemingly unrelated symptoms. Things just didn't work right -- apps would freeze or refuse to run, finder would lock up, etc. First it was occasional but within a few days it was common and everything was slowing down. Not a single test I ran found anything wrong, but I started seeing more and more hard drive related I/O errors in the system log. By the time I got home and got it to the Apple Store it was taking more than 15 minutes to boot. They replaced the logic board and the hard drive, so I can't say for sure which was bad but it was fine after that.