I was just working through Saumil's checklist again. I got down to about #40 (or so) and found slot #4 to have 12v. According to Saumil's list, this indicates a bad throttle cut-off switch. This actually makes sense (in a weird electrical problems sort of way) given the symptoms I experienced yesterday.
The A/C cut stopped working after heavy throttle, then simply did not come back on again (I realized this only in retrospect).

But now, where is that throttle cut-off switch?

-Brett