Trying to build my first pc, ran into problem:( please help

[rileyrulesu]

I Just got the motherboard and parts. During initial assembly/breadboard (on top of box) the system could not get past POST. The DR DEBUG display repeatedly cycles 10,15,19... 56,46,... 31 (pause, restart) ; (Note that "..." means "one or more codes displaying too fast for me to recognize").
I tried different memory configurations (I have two 4gb sticks) but that made no difference. I removed, inspected and re-installed the CPU, finding no problems. I have repeatedly cleared the CMOS to no effect. I installed and removed graphics cards (and cleared cmos) to no effect.
I have repeatedly checked, unplugged, and re-plugged the power connectors
I am completely stuck. The codes we've seen appear normal, except for the "56", meaning invalid CPU type or speed, which is, to say the least, ominous - but the boot does not fault at that point - it just reboots after the 31, which is memory successfully installed. Any ideas or suggestions?

For the record, this is my build

Part list permalink / Part price breakdown by merchant

CPU: Intel Core i5-2500K 3.3GHz Quad-Core Processor ($199.99 @ NCIX US)
Motherboard: ASRock Z68 Extreme3 Gen3 ATX LGA1155 Motherboard ($129.86 @ Newegg)
Memory: Patriot G Series Sector 5 Edition 8GB (2 x 4GB) DDR3-1333 Memory ($24.99 @ Microcenter)
Video Card: PowerColor Radeon HD 6870 1GB Video Card ($144.99 @ NCIX US)
Case: Cooler Master HAF 912 ATX Mid Tower Case ($49.99 @ NCIX US)
Power Supply: XFX 650W ATX12V / EPS12V Power Supply ($54.99 @ NCIX US)
Total: $604.81
hard drive from old PC.
(Prices include shipping and discounts when available.)
(Generated 2012-01-11 19:59 EST-0500)

I also RMA'd the motherboard and got a new one, which also has the same problem.

[Endless Mike]

Maybe you got a bum CPU. It happens.

[GeorgeH]

Bad RAM. Return it and get a different kit that runs at 1.5V.

[soren121]

Record the DR DEBUG display with a video camera and play it back slowly to get the codes that flash quickly.

It's not necessarily bad RAM; the Sandy Bridge memory controllers may get fried by using memory with a voltage over 1.5, but I've not seen a reputable test of this.

If it complains about the CPU type, I'd send the CPU in for an RMA quickly, before the return policy ends.

[GeorgeH]

I didn't mean to imply that 1.65V was necessarily bad (but it'd be really dumb not to buy 1.5V RAM); my logic went like this:

1) CL9 1333 @1.65V is horrible by today's standards, implying chips harvested from the very edge of usability

2) DOA RAM modules are much more common than DOA CPUs (I'd guess by orders of magnitude)

3) "56" could be normal behavior, or simply caused by the CPU's memory controller freaking out

4) The code proximate to the reboot is memory related