[kactuskid]

Neutrals and grounds are supposed to be together in the main panel, they connect to the same neutral/ground buss bar. The rule is one neutral wire per hole. Ground wires can usually be double up in one hole. But this is the ONLY place that they can be tied together.

So, it sounds like you have the early version of romex wire on this circuit or knob and tube, which has no ground wire included in the cable jacket. K&T used the paper insulator and is cloth covered. I can't figure why you are seeing a voltage reading when measuring from hot to the metal box with this type of cable installed. This asphalt covered older romex with the silver covering and K&T wiring has a reputation for becomming very brittle overtime and the insulation flakes and falls off. I'm thinking that it's possible the insulation has broken off the neutral wire where it attaches to this metal box and the bare wire is making contact with this box. This would be very dangerous cause the box is actually live then.