I have a DFI DK P35 that I just moved along with CPU/RAM to another case; I upgraded to i7, gave my wife my E6600 and bumped this dual core down to my home server. I mention all that because some of it may be relevent:
The home server was dead one morning; power supply gone. So I bought new PS and still - no post.
So I did the above shuttle, move a known good motherboard/cpu into it and still - no post. The power lights on the board light up but absolutely nothing.
CPU is properly mounted.
RAM is tight.
I even tried shorting the power switch terminals on the hypothesis that maybe the switch itself broke.