QUOTE(jimbobjim @ Sep 21 2008, 10:53 AM)

**UPDATE** My Xbox is DEAD again
Oh well guys, looks like it's back to the drawing board.
Well, there's a surprise!

The MS x-clamp doesn't have the force to bow the motherboard upwards in the first place. The reason it fails is for several reasons. Firstly when MS used the thermal pad they couldn't use bolts to hold the heatsinks down since the thermal pad is of variable thickness so needed a solution that provided constant pressure at variable height. That's why the x-clamps have a certain spring in them. Secondly the thermal pad is a terrible conductor of heat. Thirdly, some genius at MS thought it best to put a tiny GPU heatsink on and cover it with a DVD player and minimal airflow. Genius! And of course, finally, they used a BGA chip cos it was cheaper than pins.
If they'd ponied up the dough and put a decent thermal paste on they could have bolted the heatsinks down but I guess manufacturing costs prohibited that. Bear in mind this is a console that is
half the price of a PS3 (yes, I know MS doesn't have Blu-ray but even so!)
The reason this fix kinda works for a while is cos you are putting a little more pressure on the chips by adding the extra washers but it doesn't last cos you still have ye'olde thermal pad and the clamps just don't provide enough... clamp!
What you need jimbobjim, is one of these;
X Clamp Fix Kits