Bob, I suspect that Steve has it nailed. When you test a receptical, one side will be hot and the other side "dead". It sounds like your GFCI is getting power on the line side but not feeding through to the "load" side which is everything down stream. Since the GFCI did arc, I'm surprised that it operates at all. When you change it out, study the instructions and make sure you get the wires in the proper places or it's useless as protection. You might want to pick up a GFCI tester at the local hardware store, around 10 dollars, so you can test the trip function. Just using the test button on the GFCI will not tell you if it's wired properly and if it will trip when there's an uneven load applied.