OK, problem solved (I hope).
Turns out it appears to have been my trusty WD2500KS SATA drive I was using as a %TEMP% drive decided to flake out after being on 24/7 for the last 4 years or so.![Shocked :shocked_anim:]()
It was causing freakish, random bluescreens ...
Turns out it appears to have been my trusty WD2500KS SATA drive I was using as a %TEMP% drive decided to flake out after being on 24/7 for the last 4 years or so.

It was causing freakish, random bluescreens ...