LLoyd,
Make sure you check the wires that connect to your plug on the bus. I got that message one time and found some frayed wires where the bus wires were screwed to the 50 amp plug that you insert into your surge protector. The frayed wires were touching the adjacent terminal and causing the message. Just unplug the cord, remove a couple small screws and you can see the four wires that connect to the 4-prong plug.