No, my good one died by playing with 2 cores on a GIGABYTE X58 UD7 mobo....
Then my other one died on an 760 mobo.

Yesterday I tested another one (crappy) on the 760 with 1 core and then with 2 cores and then full cores on the 760 and nothing happent.....It works fine......

So I think that it's CPU's related problem....."Something" inside the cpu dies/degrades VERY FAST when palying with 2 or 1 cores without HT and this doesn't happen to all cpu's.....
My other one is still OK......