SirKronan post up your BIOS settings.

D0 Ocing seems to be quite a bit different (easier) than C0 clocking. You might just be messing with stuff that doesnt need to be touched. At 4.1Ghz my D0 is stable at stock VTT voltage.

Going to try to get my 4.2 stable. It errored on the 6 pass of Intel Burn test...I think I need to raise my QPI PLL to 1.45...Will post some results soon as I feel satisfied.