Check that the points aren't touching the inside of the cover. That would short them out and cause a problem like yours. It happened on my 400 because the new points were slightly taller than the originals. Doubling the cover gasket would solve the problem.
wouldn't this issue occur immediately though if it were grounding out? the cover is secured tightly with screws as are the points. The gasket that is on the outer edge is not in the best of condition so it could likely see replacing soon.