Ok yet another wrinkle. I had the Mac turned off for an hour or so while I did something else, came back, and now everything works. Shufflepuck, Fools Errand, Gunshy, they all work! Could my problem be heat? I had the Mac on for about 3 hours when I was having problems. I need to check and make sure the vents aren't being blocked I guess.
Tempest

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After it crashes and you turn it off and back on, do things start crashing immediately after booting, or does it work for a bit?

At this point I'm thinking that it has to be a heat related issue... maybe a bad wire, loose connection, solder joint, or badly seated chip or RAM.

EDIT: Maybe you could add a fan somehow either internally or externally... one sure way to fix the heat issue is to replace the Plus with an SE.