OK, I know this sounds STUPID, but did you press the power button in front? I know, i'm an idiot...When I first built my comp., it didnt work, got a new PSU, and reinstalled everything. I was all nervous, hoping it would work, but it didnt. I realized 10 min. later that I forgot to push the front power button, and it worked...I'm sure that's not the case for you, but it could be possible.
D
BTW, the first mobo wasnt defective, it was fried when you didnt use standoffs.