rand49er, my experience is not quite the same as yours. I had initially saw a "green" light meaning the EVSE could allow charging. I then found bird poop and washed the car off, making sure to close the charge door. I then opened the charge door and when I went to plug in, I noticed amber dash charge light. Went to the EVSE and it showed solid RED meaning ground fault. Unplugged the J1772 and noticed some water dripping down between connectors. So I dried my Volt's charge port best I could, let it sit in the sun open for a few hours, then plugged it back in. Green light on the EVSE and green light on the dash and everything was charging.
Perhaps you had some water in the charge port? I also one day found a moth inside my charge port (scared the living daylights out of me as it flew out). Perhaps some critter bridged a contact or two when you plugged in?