@Mugo:
I'm really sorry to hear your situation :-( I had my A3000 die the same way. It's still dead, and I also fixed tracks and also replaced (actually removed and inserted sockets) the entire 1MB of ChipRAM just in case that was the problem, since green screens CAN be a problem in Chip RAM. But then again, any problem in the address/data lines to Chip RAM and possibly to Buster/Ramsey will yield the same problems...
If you search my previous posts you'll see some relating to this A3000 green death.
One other thing I'd say is to definitely clean all the sockets of the socketed chips, such as the Paula etc. Just making sure. Also any socketed chips should be tested on some other system, again to make sure. I know you've probably done some of this, but just a reminder.
Good luck and do not forget to keep us up to date! Perhaps if you solve your problem it'll help the rest of us in that boat. At some point in the future I will get some time to look into my dead A3000 again. This time I'm gonna X-ray the bizatch to see if there's anything that I've missed.
Cheers