Did you use arctic silver when you put the processor on the MB.
I had similar problems a while back when A processor had overheated due to a defective heatsink/fan. The box would power up for a 1-2 sec then die. also since you received the MB back did you verify the CLEAR CMOS jumper was not set in the CLEAR CMOS configuration because if it is thats about the exact thing that will happen.
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