jezzag said:I was having the same random reboot problem as you and found putting the MCH in the bios +1.5 and upping the core voltage a notch or 2 cured it.
I must have pushed it a bit far, I've knocked the CPU back down to 3ghz, slackened the memory timings a little and upped the vcore and touch wood, seems to be fine now.
The power on, power off loop happened to me to begin with, I'm sure mine was caused by bad bios settings, I whipped the battery out, tried different settings and it hasn't done it since.