Tell us the make and model of the breakers. That may indicate that the panel was swapped after the house was initially built. The condition is dangerous for multiple reasons. When I have found this problem, it often was that two circuits went to a wall box and got tied together. In cases like this both circuits feeding that fixture(s) must be on the same pole of the service in order not to create a dead short circuit. Find and discontinue the interconnection.

Same issue here, only my breaker box is 25' from the door of my crawlspace and I got tired of going under there and quit for today. Just left the light on while the switch says off. I am sure I wired the new light the same as the old one was wired. It's the end of a 3 fixture string. There are 2 black, a white, a grey, and a ground. The 2 blacks were with the black on the fixture. The white and grey were with the white of the fixture. The ground to the ground. I mean, that's simple, right? How could I have messed that up? Now the switch is in the off position and the light is on. Turn it off and trip the breaker. Keep the switch at off and reset the breaker and it trips immediately. I plan to undo and redo it tomorrow, but I don't fathom any new result. Any thoughts and/or advice? I am not a professional but I do reviews for Kichler so I've installed and/or replaced more ceiling fixtures than I can count and thus has never happened before. Thanks- Karen

Sounds like maybe they had one wired for a night light or just miswired. The humming is probably due to the fact that they used a cheap dimmer and or lamps. A quality dimmer will most likely clear up the problem but some lamps will hum, especially when turned way down. Are these incandescent or flourescent fixtures and lamps? If they are flourescent, they may not be compatible with a dimmer.

I cannot offer much technical help, but can say that we experienced something like what you describe when we lived in western MA. During the summer, lightening hit our house, breaking a few light bulbs but apparently not causing other damage -- everything seemed to be working fine, once the light bulbs were replaced. Roughly 4 or 5 months later, in mid-December, a major snowstorm hit, during which the lights, etc. in half of our house started flickering on and off. Fortunately, a wonderful electrician lived just a few houses up the road from us (rural area) and came down during the storm, assessed what was going on, and immediately did repairs (he considered it an emergency). It involved half the circuit board of our house and, according to the electrician, stemmed from the lightening hit during the summer.