ANSWER: When you pay NGC another $15 + S&H to correct their first error

I have a 1964 Kennedy half proof that I know is better than a 64. Under magnification you can't find a single scratch (front or back). There are no spots or discoloration anywhere. I don't know enough about coins to talk about the strength of the strike, but it looks as good as any proof I have ever had. I would love to have NGC check their work, but I can't bring myself to pay them again! First, because people are reluctant to admit their mistakes, and second because I already paid them to grade this coin. If they "blew the call" I shouldn't have to pay. I think I'll just break it out of the holder and have PCGS grade it. If it comes back 64 i'll admit I was wrong!