Using points, no spark

I have a '67 318 still using points. The car ran fine Sunday morning, but I couldn't get it to start later that day and it still won't start. The engine cranks, but that's it. Here's what I know so far:

fuel is getting to the carb
The battery is new, and I've got 12v at the ballast resistor and at the coil
the points are opening and closing, and the rotor is spinning
the plugs are dry, and the spark plug wires are new, but there's no spark

Any suggestions?