Hardlock crashes, no BSOD

[Silven]

My rig has started giving me hardlocks with no BSOD that require manual shutdown. No codes are present after reboot like the ones you typically see when testing a CPU overclock. I have no idea where to start looking to diagnose the problem.

The only clues I can seem to gather are that the 3 hardlocks that have taken place today all occured while either watching a video on YouTube, or downloading a file to my HDD, or both. I actually spent the better part of 6 hours today, prior to these hardlocks, running a ton of graphical benchmarks to stress my GPU and CPU overclocks without any system stability issues. So it seems relevant that the locks seem to be taking place during mundane low-resource tasks.

One lock took place during the download of an Nvida driver (355.98, to test benchmark differences), the other 2 took place downloading a game from Steam. Pretty sure I was watching YouTube and doing some light web-surfing during 2 of the locks as well. I monitored system resources right before the 3rd lock and CPU and GPU load were both near idle, temps well under 50.

I appreciate any and all assistance.

Specs:
CPU: i5-4670k OC'd @ 4.4ghz - 1.34vcore 1.97vrin
GPU: MSI GTX 970 OC'd @ 1.48ghz core 7.75ghz memory - 1.26v 110% power
MOBO: MSI z87-g45
RAM: GSkill 2x8g XMP'd at 2133mhz
PSU: CoolerMaster G750M
OS Drive: Samsung 850 EVO 500g SSD
Storage Drive: 1TB Hitachi HDD
OS: Windows 7 64-bit

Apologies if this isn't the right place to post, couldn't think where else this would go.

 

[xapoc]

Knowing that you already run stability test, I would still default your GPU and CPU to stock on every level, then monitor the system to see if it still locks up. You wont always get bsod.