Issues OC'ing Q6600 w/ 780i

Hey guys, so I have a Q6600 G0 Stepping mounted in an XFX 780i SLI mobo, and it's currently OC'd @ 3.15GHz but I want to go higher since it's bottlenecking my 5870...but I can't. My mobo is currently set at 1.4250 V which translates to 1.360V actual (at idle, and I know, it seems like a pretty steep drop off). Problem is, I can't seem to go higher and it's not like my cooling isn't adequate (I use a Corsair H50 water cooling kit and my temps during Prime95 never broke 45C). I've read several reports where people were able to OC straight to 3600 MHz while just leaving the voltages on Auto but I tried that to no avail and I've cranked the voltage up to 1.5 V in the BIOS (= 1.448V actual @ idle) but my screen locks up after 15 seconds or so after Windows loads. CPU Thermal Control, and C1E have been disabled, as have the Spread Spectrums, and I've read several OC'ing guise to no avail, any advice is welcome!