Run a CPU stability test (Linpack / IntelBurnTest) and a GPU stability test (Furmark), but not at the same time. If the CPU stability test passes but GPU test fails then it's more likely than not that the rest of your computer is fine and changing the GPU will get your computer completely stable again.
Did you try lowering the clocks, cleaning out the card, or turning up some fans? A GPU chip can operate at the 90°C mark, but usually the GDDR RAM can't (properly).
Have you looked at event viewer at all in the administrator tools section of control panel. See if there are any errors, warnings, or criticals coming up and time coded for the times your computer is having this issue. Usually it can give you a good indication of what's causing it. I had a similar issue with my computer after rebuilding it. Random freezes and occasional BSOD's. I checked event viewer and found driver mvs91xx.sys was having issues at the same time the freezes were happening. Random disk timeouts and raidports being reset. I updated the driver but the issue kept happening. Basically the driver mvs91xx is the driver for the Marvel Raid controller in my computer. Mine was also a new build. After several checks and a week of troubleshooting I later found out that my motherboard and my separate SATA Controller card (needed more SATA slots) used the exact same Marvel controller chip. Basically because they were 2 identical separate Raid controllers in the same computer and both were using exact same drivers, it was causing hardware/driver conflict in my computer. I ended up having to take out my SATA controller card and sacrifice a drive in my computer. But the problem is gone now. I never would have figured it out had I not used the event viewer. Check out your event viewer and see if it can point you in the right direction.
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