Originally Posted by Xanthosis
Everything is reseated and new thermal paste same thing...
Have you checked for bend pins on the socket and the CPU?
You could be interested by this post also:
I had the same problem with an ASUS P7H55-M Pro with an I5-750 CPU and 8GB memory. I originally had 4 GB DDR3 Dual channel (2x2GB) and thought the memory was bad so I bought 4 more to try. 4GB showed as 2GB and 8GB showed as 4 in both the bios and Windows 7(actually windows sometimes showed 8GB was installed but only 4 was usable even though the bios always showed 4GB usable). I tried everything and searched all the message boards to no avail. Most posts point toward either a badly seated CPU or a bad motherboard trace between CPU and Memory. I reseated the CPU several times to no avail. I was about ready to give up when I decided to try the CPU one more time. I checked the socket and blew it out with air. Then I had read about a Japanese post about applying lateral pressure on the cpu (away from the locking point of the lever and towards the pivot point of the lever) as you close the CPU. I had recently got COD4 Multiplayer running on 64 bit windows 7 by plugging in a microphone, so I was willing to try anything. I applied firm lateral pressure in the indicated direction while closing the CPU holder. I also made sure the headsink was installed with even pressure. Unbelievably, this worked and the bios reconized the 8gb. Hope this helps. Not sure why ASUS motherboards seem to be more susceptible to this issue.
Read the thread also, plenty of useful information.