Hmm. Cooling. That's something worth investigating. This computer has one monster fan for the whole thing, currently spinning very slowly, but then I've recently cleaned enough dust bunnies from behind my monitor that there's every reason to include dust as a possible cause of the problem. Question to the gallery: how far into the disassembly process would you go? Getting to the point where you've got access to the internal heat sink from top and bottom is non-trivial.

Meanwhile, after running the built-in diagnostics, my computer's been much better behaved. No video glitching. We'll see if this holds up. I'm at a loss for understanding *why* a series of diagnostic tests could have positive side-effects on my computer, but... perhaps they did.