re: Why are my circuits dying?

Turns out I am a dumbass and there was a third switch on the circuit that was half-up/down. Still doesn't solve the other two circuits that went dead, but this one is a no-brainer.

As for the other two:

(A) three garage plugs, no known switches other than the panel. Dead.

(B) three can lights in the kitchen. I change the dining room circuit to rheostat and suddenly the three cans in the kitchen die. I change that dining back to a switch, kitchen still dead. I back feed off the neighboring circuit to get some light. On to the next fire.