If you ran a new line and put a GFI breaker on it, the neutral from the receptacle does "not" go on the neutral bar in the panel. It goes on to the neutral terminal on the GFI breaker.I ran the line and added the breaker so I know it's hooked up like the rest of the panel, the white and neutral are in the ground bar and the black runs into the breaker.
There should also be a white wire coming off the GFI breaker which goes to the neutral bar in the panel. Not the ground bar even though they are connected together.