So I thought, thought, thought. Then it occurred to me that this all started during a day-long thunderstorm. Well, perhaps the power supply was dying, I reasoned. So I did some emergency computer transplant surgery and replaced the psu with one from an old computer... and, so far, it's working fine!
My god, am I amazing!
Also, I'm just polishing up a new short story I'll be posting soon. No spoilers, tho!