I have a very similar condition. On a new pc I finished about a week ago, my mobo (Asus Rampage Formula III) only sees 8gb of the 12 gb of RAM installed (but no other problems). I read that simply resetting the CPU often fixed that problem, so I remove the Corsair cooler installed, reset the CPU, and replaced everything. Now it won't POST at all, no beeps, no CPU LED--although all the fans run fine. After reading your post and some other threads, I wonder if the problem might be between the CPU and the heatsink--I think I maybe was a little too careless about removing the old paste and replacing it evenly. It seems that sometimes makes the CPU refuse to work. Tomorrow I'll try replacing the paste and reasssembling the thing, and let you know if that helped.
For anyone else--if my CPU had been "fried", would that leave visible damage? Because when I checked it again all the contacts looked fine.
I replaced the thermal paste following the directions on Thermal Arctic's website very carefully--no change. BTW, I discovered my system will also only shut down using the main power supply switch.
Here are my components:
ASUS Rampage III Formula
Intel I-7 970
ATI FirePro V5800
Cooler Master H50
Cooler Master Silent Pro M700
Cooler Master HAF 932 case
Corsair Vengeance 12gb DDR3
As I said, other than only 8gb of RAM being detected (by both BIOS and Windows 7) everything was working fine till I opened the case and reseated the CPU. Now--nothing. Despite the difference in components, it sounds very much like X-2's problem. And like him, I've tried the steps in the other thread (I'm awaiting a power supply tester I ordered) and nothing has worked. Anyone else have any ideas for either of us?
The problem was the motherboard. I'm not sure how I missed it before, but there were about 10-12 pins in the cpu slot that were bent. After trying unsuccessfully to bend them back, I screamed a little bit, then went out and replaced the board. Everything now works--I even realized I had the RAM in the wrong slots, and fixed that problem. But it was an awfully expensive lesson.