Occasionally when fueling, the gas will back up long before the tank is full, usually overflowing onto the ground (very frustrating these days!). When this has happened it would back up repeatedly until I finally gave up and drove away without completing the fill up. I finally tried starting the engine momentarily, which then allowed the gas to flow into the tank.
Does this sound like some kind of vapor lock in the filler line? Any theories/remedies? Could there be a blocked vent hole somewhere?