Same problem. I spent around an hour on the phone yesterday and the support person (Pamela) carefully listened and worked with me on this. She didn't understand what the problem is, as she was following the logic. We also tried different numbers and the only one that worked was when we Zero'd out the amount, but then my tax credit disappeared. This is very frustrating and I'm still waiting for a call back. My guess is they don't have an answer yet, but it seems that its a coding error?
