Really WEIRD electrical problem

Sorry this is so long but I need to describe the whole thing.
After an electrical storm, one of the kitchen GFIs was tripped. Everything was unplugged from all receptacles on the circuit. When the GFI was reset the breaker tripped. Resetting the breaker caused the GFI to trip again. This cycle was repeated several times.
Then it changed so that turning on the breaker caused the breaker to trip immediately.
With the breaker off, a working ohm meter showed no connection between the hot and the neutral or ground. So it appeared as if either AC or a higher voltage was required to see a short & trip the breaker. (Remember this whole thing started during a thunderstorm).
I started disconnecting the receptacles & junction boxes one at a time trying to isolate where the problem was. I saw no damaged wires. I did not know the order in which things were connected so I'm sure the order I did the disconnects was not the best.
Eventually I could turn the breaker on without it tripping so I started connecting things back one item at a time, testing after each reconnection until everything was connected as it originally was. The problem was gone. I tried wiggling the wires I could reach but the problem stayed fixed. That was several weeks ago.
Now, immediately after another electrical storm the problem is back.
What is going on? In giving an answer, please keep in mind: 1. The problem has appeared twice following a severe thunderstorm 2. An ohm meter showed an open circuit but it acts shorted under 120 VAC 3. No apparent physical damage to the wires. 4. The breaker stays on with the GFI connected but nothing downstream connected. 5. The problem went away (until the next sever thunderstorm) after dis/re-connecting everything.
MANY MANY thanks for any help.
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Thanks for your reply. I will do that. Something of that sort is the only thing that makes sense to me. Could the burn hole be invisible because it is through the black insulation in a spot that is covered by the yellow (#12 wire) insulation?
On Mon, 29 Jun 2009 22:01:49 -0500, snipped-for-privacy@invalid.com wrote:

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On Jun 29, 9:23 pm, snipped-for-privacy@aol.com wrote:

Considering cost and time...how about replacing one or all of the GFIs. It's possible that sensing circuits have become burned or marginal.
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Thanks for the reply.
As stated, the only GFI on the circuit was replaced with no change in symptoms. It was also mentioned that there was no problem when the GIF was in the circuit but everything downstream from it was disconnected. This makes it hadr to believe the GFI is part of the problem.
wrote:

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On Jun 30, 8:34 am, snipped-for-privacy@aol.com wrote:

I see nowhere that you changed the GFI !? Maybe I am blind !
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Do you have any power strips with surge protection?
These work by shorting the lines to each other and to ground. They can go bad after a surge.
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On Jun 29, 10:23 pm, snipped-for-privacy@aol.com wrote:

re: 5. The problem went away (until the next sever thunderstorm) after dis/re-connecting everything.
Have you considered water as the cause?
No rain, no rainbows. I love that commercial.
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Since this is an unusual problem and normal diagnosis has not found the problem, the next logical step is to start replacing things, cheapest and easiest first. Since you have replaced the GFI, the next logical step is to replace the breaker. Once components are eliminated, all that is left is the wiring.
If you can borrow a "megger", it checks insulation at higher voltage, typically 500 volts. They will often find charred insulation. They are commonly used in industrial electrical work and electric motor testing.
Don Young
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The second time the problem appeared it didn't go away and I was able to isolate it to a peice of wire about 4' long in a wall which I couldn't access without opening the wall. The modular manufacturer will have to deal with it.
I was able to temporarily wire around the defective piece of wire.
Thanks for all the suggestions.
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snipped-for-privacy@aol.com wrote:

Hi, I'd suspect GFI(s) in the circuit. And I'd use analog meter such s Simpson 260.
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