3 iMacs and a iBook :)

As for the iBook, try putting a shim on the video chip? That seems to fix a lot of them, so give it a try.

buy a plate of sheet metal and cut the shim in to a square a big as the square on the heat shield ( you will see what i mean when you open the machine up ) place the shim on top of it close the machine up dont screw it down see what it does continue in this fashion untillthe bleeder works ( or until the shell doesnt fit any more then its really dead ) affix the shim with some aluminium tape and it will ...work ..for a whil

think about investing in a paint stripper

I tried 4 thick pieces of card paper. Stayed on for-1 min?

It has a ATI Radon 7000 with off chip memory.

Why does that chip fail? Heat?

paper isnt good enough its not rigid enough not does it provide enough pressure you need plastic or sheet steel

the chip is failing because the bal grid array solder is becoming unstuck

it needs to be reflowed either profesionally or do it your self

the shim is only temporarily because it forces the solder to make contact again but eventually it wil begin to crack and deteriorate