Data entered into fields disappearing

I just installed WooCommerce to two of my websites. On one, on the billing and shipping page, the customer can enter the information and it works just fine. On the other, when you entered in “first name” and then tab to “last name”, the information entered into the first field disappears. If you go back to it, it is there, but when you tab away from it, it disappears. I have no idea of what to do. i have compared the settings on each of the sites and they both appear to be identical. Any ideas??