Pb Pismo external cache failure

Long time reader,first post.
Yesterday I was in a shoppingmall surfing the internet and got problems with startup disk.
I switshed to my second partition and it also got problems.
Then,I had an external drive startup and it too failed after a while.
What happened is that it seemed like it was stuck but still works until it eventually got completely stuck.
I know when a disc is almost full U can get the same thing going on because of virtual memory filling up the disc.
This is not the case though,all of these discs had sufficient space left.
After arriving home I luckily found another external disc with OSX 10.4 and started up from that but got the same problem.
I can't use a cd to boot from,my drive doesn't work.
I was almost there to repair my disk with discwarrior but just before it got stuck again.
After starting up and starting verbose I saw though that it failed the selftest and I could even go into system profiler and saw this:
Diagnostics
Last run : 1/1/1970 07.00
Result : Failed
Failure type : External Cache
Sometimes with a fourth one:
Memory slot : SODIMM/J1
I changed my internal harddisk,swapped Ram from one to another slot but to no avail,still having the same thing going on.
Did a PMU reset,removed power and battery,pram reset,booted into OF and did set default-reset nvam-reset-all,all to no avail.
Now,I think myself that it's gotta do with my processor board,cache broken.
But,could a badly cooled processor be the problem,there was little paste there and also a bit hard.
My Pismo is already old,almost 8 years,changed logic board once,secondhand display,been using it over 15000 hours!!
I want a new one but,I don't like so much the new iMac and I live most of my time in Indonesia and the 250 watts the iMac uses is a problem.
Does it consume that much or is this max?
When can we expect an iMac with Oled display and would that be much less power consuming?
Another option,Macbook + Display but I don't like the 13" screen,Macbook Pro + screen is Cash=++++,Too much.
I am sorry I asked so much but I need some Pro thinking here,any advice is welcome and mostly appreciated.
I'll be back here tomorrow,internet is cheap in cafe's but in the 50-60 dollar range for 512 Kb/s connection,outrageous.
Cheers and thanks

Enjoying Macrumors a lot!

P.S. What is DMA failure(harddisk)

 

Cleaning with alcohol failed

I found some information on the net suggesting cleaning the board with alcohol but that didn't work.
Better keep it for pleasure and get pissed so I get over it
I will go to Singapore in a couple of days,anyone any knowledge of finding a second hand hardware store for Apple there?
I will be buying a new mac but I prefer to wait untill I can get a iMac with Oled display.
Cheers

Oh,BTW,I read about Oled now and they don't seem ready,I think I meant led backlight,sorry for that.