Tito SwinefluI have one circuit in my house that runs 3 overhead lights and a wall outlet. Yesterday, it suddenly threw the breaker, nothing weird was happening, I was just sitting there.
After a bit, I managed to narrow it down to one hanging light fixture, which was installed a year ago. You can see in the video - I first check that the light bulbs are good in a different fixture, then I try to screw them into different sockets in the chandelier while it's energized. When I do that, an arc happens and the circuit breaker is thrown. Happens in all the sockets.
Again, NOTHING has changed in this circuit, this chandelier has been sitting there like this for a year, and all of a sudden, this. Why?
AZ Guy 
@tito_swineflu I wonder if the chandelier ground wire is connected to the hot? I wouldn't touch it without the breaker off, could be dangerous.
@az My next step is to remove the fixture, but it would be weird for it to be wired correctly and then suddenly, a year later, no longer be wired correctly.
@tito_swineflu Could the bulbs be screwed in fully with the power off so that they don't bump the chandelier body?
@az No, because any bulb screwed in all the way will cause the circuit breaker to trigger. If I turn off the circuit and put in one bulb, I can't turn the circuit back on because it's shorting in the fixture.