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I had the same problem for a while, I switched outlets and let my charger sit (outside the outlet and not connected to the computer) for a bit and the problem went away.
 
I would talk to someone at the Apple store.

I experience dim green light too sometimes, usually for a few seconds when I plug it in, but then goes to normal. Not worth taking it in to Apple since I have no warranty, and everything seems to work ok. But I would like to get more info about it.
 
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