Intermittent Boot....Lots of details

Just received my rev 3 p67 board and have been in the process of getting the my machine up and running again. Here are the build details:

Case: HAF922
PSU: CoolerMaster Silent Pro M 700w
Mobo: Asus P867Pro Rev3
CPU: Intel Core i5 2500K
Memory: Corsair XMS 8 GB (2 Dimms)
HDD: WD 1TB Caviar Blue (to be swapped for SATA 6gb/s when next gen comes out)
Optical: Lite-on BRD Drive

I purchased the system at the end of January. After build everything worked perfectly and the system worked like a dream. One day after about a month of solid use, the machine no longer was passing POST. All I got was a bright red CPU LED lit up.

Attempting to fix it, I first laid it on it's side and hit the power. Booted fine...the first time. Subsequent boots however failed. Because my RMA mobo was on it's way, I decided to just leave it be for the time being since I was going to have to take it apart anyhow.

Rev3 board comes in. I take out the old one and pop in the new. Boot the machine, doesn't past POST - same CPU LED. Frustrated I leave it for a week. Coming back to it, I again put it on its side and boot, this time it works. Odd. Try again, same thing. Stand it POST success.

At this point I think it's a short. The Mobo is new, so i figure it's not that given the behavior is identical. Hypothesis at this point: perhaps it's the case or something that's touching something else and causing it to short.

So I pop out the mobo, put it onto some anti static wrapping with the memory, cpu, and case front panel LEDs and switches attached. No Good. So I remove all the case front plate connections aside from the pwr swtich. It boots! I try it a number of times and it seems solid.

Put the mobo back in the case and try. Success! At this point I feel pretty confident and start plugging things in one at a time to test and see if it passes POST. Nearly everytime I plug something new in it fails. But trying again immediately after we seem okay and it passes post.

At this point I have fans, cpu, memory, and all front case things plugged in directly (not through the Q-connector thing Asus provides). Next I try to plug in the HDD and Blu-ray drive. Fails. Try again. Start. Try a third time to be safe. Fails. Unplug HDD and BRD drive. Plug in GPU. Success! Again. Fail. Success. Fail. Fail. Sixth boot CPU LED blinks and then goes off, but this time it hangs on the DRAM LED.

After a number of more boots, it seems to boot every third time. For giggles I plug in HDD and BRD Drive again. Boots 1 in 10 times, and 1 in 5 times it hangs at the DRAM LED and not the CPU LED. Tried this about 20 times until it seemed to never boot.

I have only a single guess at this point, and am looking for some advice. My guess is that it is the PSU. Why? The only pattern I've noticed is:
-When it boots, the CPU fan speed seems lower
-The more things plugged in, the lower the likelihood that it boots

Anyhow, any help would be greatly appreciated - thanks all!
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More about intermittent boot lots details
  1. Because your system sometimes works, you should repeat the steps in the following troubleshooting procedures several times.

    Work systematically through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

    If not, continue.
    The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

    Breadboard - that will help isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

    Make sure you plug the CPU power cable in. The system will not boot without it.

    I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

    If no beeps:
    Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

    At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%. If you have a white wire (many modern PSU's do not), it should be -5 volts.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    If the system beeps:
    If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

    Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

    Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
    At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

    Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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