Possible motherboard/processor issue

[batteryLow101]

Problem
I've been having issues with the computer I built about 1 1/2 years ago, and I think it may be an issue with the motherboard but I'm not sure.

Every once in a while, the monitor would go black but I could see the mouse cursor in the middle of the screen, and the computer wouldn't respond to the mouse or the keyboard, this happened when I was reading some document, when browsing the mmo-champion forums, and a few times when I was playing games. No blue screen. I had to hold down the power button to shut it off.

One time, after restarting the computer, it showed the recovery screen on the BIOS stating that there was an issue that might have been caused by overvolting, which seemed kind of odd because the voltage was set to 1.345v for the 4.4ghz overclock which isn't all that high for that processor (standard was around 1.255v before I OCed it), note that I had the voltage set to auto. I decided to just drop the clock speed back to the stock 3.3ghz.

About a month ago after booting up the computer like normal, it decided to shut itself down 2 seconds after the button press, and when I rebooted, it was stating the same error, even though I had left the clock speed alone at 3.3ghz. When I went into the BIOS settings to check the voltages/other settings, it had decided to use 1.320v for stock clock speed, which seems really high for no overclock at all. Also, the base clock set itself from its original 100.22mhz to 99.86mhz, which has me worried.

Some thoughts
Now I've been trying to determine what could cause this, first I thought I just got unlucky with the processor lottery, but after reading into it more I think it might be an issue with the motherboard, which is a Z68XP-UD3 (Gigabyte). The motherboard actually came recommended by someone from the mmo-champion forums when I was looking for build advice so I picked it up without reading too much into it, but after reading some of the more recent reviews (on newegg), people are reporting boot loop issues, which sounds similar, though not exactly, to the problem I'm having.

I could replace the motherboard, but it might be the processor. I don't want to spend a bunch of money on a new mobo or processor unless that's actually the issue (I currently can only afford to replace one of them).

Thanks in advance for any thoughts/help

UPDATE: 8/9/13: I've just booted the computer up again, and went into the BIOS settings to check out of curiosity, and the BLCK is now 99.80mhz, and the DRAM voltage set itself to 1.512V, and when I first went into the settings where I can adjust the frequencies, there was another blue message box in the middle of the screen saying the "computer recently from an issue that might have been caused by overvolting" which before, only happened after crashing from an actual overclock (note there is still no overclock on this system as of right now).

Has anyone ever had issues like this before? Anyone with the same MoBo or processor?

At this point I'm fairly confident it's the motherboard causing issues but I want to be sure, and if that's the case I'd rather just get a new MoBo than deal with the same issues if I RMA it and it ends up being a design flaw with the MoBo.

UPDATE 2: 8/9/13: I went into the BIOS and loaded the failsafe defaults which seems to have made the voltages and BCLK return to normal (1.240v vcore, 100.32mhz BCLK) for now, no idea what the issue was, as I didn't modify the BIOS settings beyond the CPU multiplier and the XMP profile for the RAM when I first set this system up (even though I had reset them back to normal manually later). I will update the OP if the system crashes again with these settings.

[batteryLow101]

I just went back and edited the OP and added some new information.