Event 41 (63) Kernal Power Critical Error -- Spontaneous Shutdown -- Help!

As the title suggests, my much loved system has decided to board a one-way train to struggle town... I'll break the issue down into as much detail as possible and then any help you guys can provide would be eternally appreciated.

I built the system for myself around late October last year, no issues, worked like a gem. I only had very minor issues with it in the following 12 months, such as occasional high case temps and a WD Hard Drive being abnormally loud, both issues were easily fixed by purchasing extra fans and going through the RMA process with the HDD. However in the last 2 months or so, my beloved system has been sporadically shutting off, and when I say shutting off, I mean one millisecond it was on, the next the system was completely shut off, so no warnings, shut down procedures or any other kind of activity. It's almost as if it just lost power, which it didn't (I don't think?). What it does after it shuts off, is, I think, the key to finding the problem. Once the system shuts down, it tries to start itself back up again - but fails 99% of the time. Basically it will turn itself back on, but crash somewhere between startup and the login screen. It seems to just get stuck in this loop of startup, shutdown, startup, shutdown, startup, shutdown etc. The longest I've left it to it's own devices is about 10 minutes, at which point it was too painful to watch so I was forced to manually shut it off. Sometimes it'll make it to the login screen, at which point I attempt to log in but it usually crashes before it loads the desktop, unless of course it's that 1% of the time and it works fine. The next time I am able to login and get to desktop, I always check Event Viewer, which always has the same critical message: Event 41 (63) Kernal Power.

Here are the details:

- System
- Provider
[ Name] Microsoft-Windows-Kernel-Power
[ Guid] {331C3B3A-2005-44C2-AC5E-77220C37D6B4}
EventID 41
Version 2
Level 1
Task 63
Opcode 0
Keywords 0x8000000000000002
- TimeCreated
[ SystemTime] 2013-12-08T05:33:08.966402600Z
EventRecordID 27054
Correlation
- Execution
[ ProcessID] 4
[ ThreadID] 8
Channel System
Computer NZXTPhantom
- Security
[ UserID] S-1-5-18
- EventData
BugcheckCode 0
BugcheckParameter1 0x0
BugcheckParameter2 0x0
BugcheckParameter3 0x0
BugcheckParameter4 0x0
SleepInProgress false
PowerButtonTimestamp 0

What was I doing at the time of the shutoff I hear you ask? A variety of things: heavy gaming, internet surfing, watching a movie, in fact it even happens if the system is just sitting idly while I'm playing my Xbox right next to it. Next question you're probably thinking is, does it shutoff after a certain amount of time, perhaps indicating a overheating issue? Nope. Sometimes the system will function without a hitch for a whole day, maybe 12 - 15 hours, no problems. Other days it might be fine for a few hours, or even just an hour before it starts shutting off. Some days the system will just start shutting off as soon as you turn it on, when it's been off for 12 hours so there is no way the system overheated. Now, I've found the best thing to do is go entertain myself for an hour, then come back and try again which has had a plethora of results. Often this seems to work as the system will start back up, but for how long? Sometimes the rest of the day, sometimes just an hour. So basically what I'm telling you is there is no rhyme or reason, that I can find, that explains why the system is shutting itself down.

What have I done so far? I have tried a number of different things. The first thing I did was always monitor my case temps, no components ever reached over 60 (Celsius), so that ruled out any overheating issues. Next I followed Microsofts advice a did a Memcheck on my RAM, came back all clear, but just to be sure I downloaded a third party version and re-ran the test, also came back all clear, so I ruled that out. I then tried a fresh install of Windows 7, no luck there, it started shutting itself off a day later. I've, very closely and carefully, gone over every PSU to component connection three times, made sure nothing was loose or damaged, again no success. My PSU is a Corsair AX760i and has an inbuilt safety check, you click the button, if the LED goes red it has detected a fault within the PSU, but every time I run the test, before and after shutdown, the LED always remains green - this would suggest that the PSU isn't responsible. I was also told to reinstall chipset drivers because missing or corrupt SM Bus Controller drivers can cause random shutdowns. I went ahead and re-installed however this proved unsuccessful as well.

Last but not least... here are system specs: http://bit.ly/IyQG1A

Please ask if you need any other details, or if I have missed anything!

Any help would be appreciated!

Cheers,
chucklehead