Nothing is logged, it just powers off.
I've run Memtest on it for a number of cycles and it comes up clean.
I figure that either:
A) Memtest is wrong and there's a bad memory spot that only gets hit occasionally
B) There are thermal problems.
C) I have no other ideas.
Any opinions from the crowd?
(I'd love a resounding "It's the memory!" as getting to the heatsink to re-thermal-paste this is a challenge", but I'm not expecting it.)