i don't know if i can help it sounds like you know what you are doing. i have had many cpu's in my bx133 no problem. i would
start it up with the 566, then shut it down. change the cpu. start it up holding the insert key. if this does not work, start it up, then kill the power to the box; do this a few times, abit says up to 5-6, but usually no more than 3 times has done it. then let try the insert key again. as soon as you here the cpu detection 'beep' hold down the insert key...this will force the boot at least. if you are not quick enough to get into the bios setup let it boot then hit the reset key, and after the 'beep' hit the delete button to get into the bios setup. i would set user define and 11*100, the with default v of 1.75.
i have abuse board and cpu through overclocking and never had as bad a problem as it looks like you are having: could it be a bad cpu?
btw, you ought to have gotten a tualeron instead...oh well, if you have to rma it maybe you can get a 1.1a.
good luck...