Overheating is the obvious one, but since you've been checking that, possibly not.

How big is your power supply and what sort of brand/quality is it? I only ask because perhaps it's related to that and the graphics card needing more power to do something quick and the PSU isn't handling it very well.

I was actually having this problem recently myself in that occasionally I would get random lock ups and something even reboots multiple times in a day and I eventually worked out it was my 5+ year old power supply. Even though it was a good brand and 1200W of capacity (about 800W more than I actually needed!) it had basically gone bad over time. I replaced it with a new one and since then haven't had a single crash/reboot. I appreciate that's not an easy thing to check though as who has a spare PSU? But if you have monitoring software that logs the voltages to disk you could see what they were before it crashed (maybe if it saved in time). Sorry I don't know any software off top of my head that could do that, but I'm sure there are some).

Before you do any of that though, might be worth just checking your RAM isn't actually faulty (although I'd expect that to more crash the game than the whole computer, but anything is possible!). I'd recommend either using Memtest86 or Memtest86+ (there is a difference believe it or not). Personally I use Memtest86+ and you basically either burn it to a CD or use the USB installer to put it on a blank USB drive and then boot from either and it'll just run. By default it'll just start an automatic test so you don't need to select anything. Although you should let it run for entire duration (may take a while), in my experience, usually bad RAM comes up with errors fairly quickly so it'll be pretty obvious pretty soon if it's RAM related.

Quote Originally Posted by Melichoir View Post
I have run the Steam cache verification to check for corrupted files. While Steam had found unvalidated files, after steam redownloaded and replaced those files, the crashes still continue. Steam seems to not carry the full date version, so it will always apparently find 44 unvalidated files?
That's because Steam has a copy of the game (from around 2.1 I believe), it doesn't update via Steam so when you verify files it actually rolls your client back to 2.1 (or whenever the Steam version is) and then the client itself will update those files back to 2.5 (big downloads!). So basically you can't use that feature of Steam because it won't work for any game that updates itself outside of Steam as it will always find invalid files as anything newer/downloaded in the game won't match what it thinks that game should have so it'll try and redownload them - Hope that makes sense?

Hope this is of some help!