After reading Tyke's post 1280 I tried some of his settings as I have the same CPU.

Kept LLC DIS and Vcore at 1.3875, NB=1.50 & SB=1.55
Changed PLL & VTT back to AUTO
Changed GTLREF0 to -14mV
Changed to 15.17 chipset drivers.

Now 11 1/2hr prime stable with manual halt, previous best was 11 minutes ending in hardware failure.

Big thanks to Tyke !!.

PS. Just ordered Asus 280 GTX TOP

My rig :QX9770 on Thermalright Ultra 120 Extreme cooler:
EVGA 9800 GX2 SSC. Creative X-Fi Elite Pro.
OCZ 4x1Gb PC3-16000C9 2000Mhz Platinum EB
Samsung F1 1TB & 2X500Gb Hitachi SATA 2.
2xSamsung 20XDVD-RW SATA
Vista Ultimate 32bit

Settings : 430x9.5=4085Mhz overclock. 1720 FSB Syn & Linked.
Mem : 7-7-7-22-30-1T @ 1.9v

Benches : 20,419 3dMark06 7,274 PCMarkVantage.