I'm really sad now ... my original Z620, which is a very early block 2, and upgraded to dual E5-2637s ... also just failed. I though pulling the daughterboard might help, and it ran for a few hours (enough to pull some files off) but now just red led of death.
I will try a PSU in it, but not holding out much hope.
I guess 5+ years of solid service is pretty good!