Previously rock solid MacPro ('08) crashed and now will not boot up past a screen of black, grey and white blocks covered in pink artefacts. Lion recently installed. Can this old warhorse be saved?

Question

Yesterday the trusted and loyal MacPro froze and on reboot kept going straight to a screen which looks like a modern art collaboration between Kasparov, a robot and the ghost of Jackson Pollock. You can see the artwork in the pictures below.
Lion has recently been installed.
Main programmes used are Logic and Final Cut Pro.
I have taken the machine apart and dusted everything down, talked sternly to the ciruit boards, offered bribes to the CPU and even played it Salsa - I figured that this works in breaking the spirits of kidnappers, so it may work with the hard disk.
Nada.
There is a suspicion lingering that the computer was aware of a make or break week of editing coming up and decided to stop working in protest (it is getting on a bit), so I let it rest for a bit before trying another reboot.
Still no luck.
Short of going Basil Fawlty on it, is there anything I can do?
Help!

Answer 1

Time to put it aside to pasture.... the 8800GT has some known issues.
Better to replace it now while you can.
As for your system, w/o another gpu but I'd give 99.999% that you are fine.
For dust I juse a powerful 500W.
http://www.amazon.com/Metro-Vacuum-ED500-500-Watt-Electric/dp/B001J4ZOAW/
Other than the card working its way loose (hard to do) or the 6-pin aux power cable being loose etc.
Someone said that "post Lion" that many Mac Pro owners have not been able to use their OEM DVD with Apple Hardware Test (the test is on a hidden partition).
$249 isn't totally bad investment to keep it running.
Other than FBDIMMs self destructing and being fried @ temps above 72*C and having errors of some sort... which is also solvable.
And while / IF you can, make sure you have made bootable clone of your system and data, and have some kind of current TimeMachine backup.