Mike... I have this problem too. Fluctuating vcore is the main issue here.
Here is my story: I use paint tricked to modify P4 1.8A processor with 1.700V as default voltage, and I also set the vcore to AUTO in P4PE's BIOS. At the begining, the BIOS and Asus probe reported the vcore of 1.789V (over-voltage) for 2 or 3 days. Everything went smoothly, and overclocking well up to 145FSB.
After a week passed by, my existing OC setup went bad , and I got the problems like yours, BSOD, crash, won't boot, etc. Fortunately, I noticed the VCORE reported by BIOS is now lower 1.522V (under-voltage). I said WTH??? after tweaking this and that..... I finnaly gave up. I have to satisfy now with 135FSB instead.
Solutions: I think you need to increase the Vcore more in BIOS and watch the Asus PC Probe. If you are sure that your mobo is under voltage, you can set it high, for examples. 1.800V ?