Hi again,
have just repaired another x360 (Error 0102) with Hot Air Gun!!
This box was really dead, no sound and screen only 3 red blinking leds. So I used the same method as I wrote in my last post.
x360 boots now just fine, no problems at the moment. also played 5 hours without stops!! hehe
Would be very interesting if somebody could repeat that and port his results.

i followed your advice and used a heat gun on my bga ram chips and southbridge as well. the first run i used a fairly low temp and a quick try proved correct. it powered on and made it to the dashboard. roughly 3-5 minutes later, it froze. that simply backs up the theory about the ram chips being poorly attached and/or poor quality chips.
IMHO, from the behavior the system exhibits, many 0102 failures are due to bad RAM or RAM that was damaged by exposure to heat. Try to think about this more from a planar point of view and less of a console. when a motherboard fails to POST, we tend to trouble shoot Physical Damage->BIOS->RAM->CPU (in no particular order). once you've ruled out physical damage and since in this case there is no adjustments to be made to the bios, RAM/CPU are the next logical areas to troubleshoot. by simply looking at the design of the heatsink for the GPU, it should be fairly obvious that there is indeed a heat problem where the chips located under the heatsink are exposed to higher temps w/o any benefit of the heat sink just milimeters above it. personally, i'm going to send mine back to MS and get a refurb. i'm curious to see if anyone has chopped off their GPU heatsink to expose the ram chips below, and added a fan to it. Even adding some sort of heatsinks for the remaining RAM chips exposed on the top of the planar like the ones referred to in the above post. Anyone wanna give that a shot and post the results?