shutdown SOLVED , sensor cable in cause
among all solutions proposed over the web, who tried this one, which seemed to be working fine for the few users having tried it (but loosing apple’s warranty…)
http://maba.wordpress.com/2006/09/01/macbook-shutdown-solved-at-last-hopefully/
people who have put an insulating scotch on the sensor cable didn’t experience any shutdown since. didn’t receive my mackbook yet but if it ever shuts down i will try it for sure, since apple doesn’t seem able to fix the problem permanently. People get computers back from repair shuting down again and again.