Unable to get stable overclock on i7 920 / Asus p6t

I'm new to overclocking, so after trying various 3.6ghz and 3.8ghz overclocks and being unable to get them stable, I decided to start less ambitiously and simply try 3.3ghz by leaving everything on auto and simply raising the BCLK to 166. (I've heard in numerous reviews that this was the simplest approach to OCing this cpu/mobo combo, however last night something went wrong...)

This ran stably for several days for running games, etc, so last night I attempted an overnight run of Prime95 to ensure stability. I woke up this morning to a BSOD, which is baffling to me. Any ideas why this may have happened? The only other change in the bios besides the BCLK was manually changing my RAM timings to 8-8-8-21.

Thanks for any input.

CPU: i7 920
mobo: ASUS P6T
RAM: G.SKILL 6GB (3 x 2GB) DDR3 1600
VGA: EVGA GeForce GTX 285
Case: COOLER MASTER HAF 932
Cooling: XIGMATEK Dark Knight-S1283V 1x 120mm
PSU: CORSAIR CMPSU-750TX 750W
HDD: Western Digital Caviar Black WD1001FALS 1TB 7200 RPM SATA
OS- Microsoft Windows Vista Home Premium SP1 64-bit

Have you checked the Memory settings? I selected a slower memory so my 1600Mhz is running at 1480Mhz instead of 1600Mhz. I can use tighter timing which give overall better performance. Once I turned the RAM speed down my system was much for stable. I now have the same system as you but overclocked to 3.7GHz Prime95 stable.