Sorry to be late getting back, but the good folks at Tasca Ford diagonosed the problem and repaired it in one day!
They told me that a wiring harness near the power distribution box was rubbing against an AC line and shorting out.
Total cost of repair: $250
I've since looked around the engine compartment but cannot see where they made the repair.
I still have to wonder if it was the rats that chewed through the wires...
