Guys, I got the sudden problem.
I have been using my new E8400 E0 for 6 weeks. 500x8 @ Vcore=1,160. I stressed it with Lipack, Prime95, MemTest3.8, OCCT, SuperPi. Absolutely no problems, BSODs. Full stable. But now I can have 2-3 automatical reboots per day. I decided to encrease Vcore by 3 notches up to 1,192. It seems the problem have been resolved.
Is it possible my chip "degradated" and now it needs more volts?