Nokia has officially admitted the power problem in a no. cases of N8 handset not switching on or "dead". But the problem is covered by warranty and replacement will be made if not reparable.
http://seerpress.com/nokia-acknowledges-defects-in-some-n8-devices-offers-replacement/14583/
http://infocera.com/Nokia_N8_power_problem_genuine,_admits_Nokia,_covered_by_warranty__10953.htm