Thank you.
It turns out that I was misreading my 1040X return... Line 23 is the line to apply a portion of your refund to future estimated taxes. But the amount field for that line is blacked out, you cannot enter an amount there.
I must have scrolled past the end of the 1040X and was looking at the original 1040 form where I had applied my original refund to future estimated taxes. I got the refund I was due, and TurboTax did not make a mistake.
Dave
