PC failing to boot

[parkcarshere]

Well, failing to boot *sometimes* I guess.

I built my PC last December and after a few issues with my MOBO which ended up with me getting two replacements, everything has been working fine. However, about a week ago I turned on my PC and noticed that the monitors never came up and showed the BIOS. My mouse is a Razer mouse so it was lit up, indicating everything was getting power, but no BIOS. So I held down the power button, shut off the PC, and turned it back on. Everything booted up fine, and I forgot about it.

Unfortunately, this has been happening every day for a week now. Everytime I get home from work, I turn on my PC, and I usually need to power it down once (or, as is becoming more frequent, power it down twice...) before it finally boots to Windows. Once it's up and running, it has no problems whatsoever from what I can tell.

Any ideas? Is this another sign that my MOBO is dying yet again?

This is what my build looks like:

OS: Windows 7 64-bit

Video Card: GIGABYTE Ultra Durable VGA Series Radeon HD 6850 1GB

Motherboard: ASRock Extreme3 870

RAM: G.Skill 4gb 240-Pin DDR3 1600 (Four 2gb sticks for 8gb total)

PSU: CORSAIR 750W

HDD: WD Caviar Black HDD

Shouldn't matter, but to be comprehensive...
-DVD Burner
-Cooler Master CM690 Case

 

[parkcarshere]

I would like to add a little information to my initial description:

I discovered yesterday that if I restart my computer from Windows, it will also exhibit these problems - staying at a black screen until I shut off my PC one or more times, at which point it finally boots.

Also, one thing I've noticed that if I turn on my PC and it boots to Windows on the first try, it always blue screens shortly after being in Windows. Then, it usually freezes while dumping the physical memory at about 80-90%, at which point I shut off the computer and start the restart process again.

After either of these things happens [A) not booting until restarting twice, or B) starting, bluescreening], the PC runs perfectly fine until the next time I turn it off.

 

[parkcarshere]

Some more information:

While using my computer today, it my screens went completely black as if it restarted. This is the first time it has happened while actually using my computer - usually it just happens when turning it on.

This time, I opened up my case to see if there were any diagnostic lights or anything to give me a better idea. I found out that when it "freezes" at the BIOS, the Dr. Debug light is stuck at D5, which in my manual says "Bootblock code is copied from ROM to lower system memory and control is given to it. BIOS now executes out of RAM."

So, I was pretty sure it was my MOBO... but does this mean it's my RAM that's dying?