Safari Incorrect Stored Password Causes Endless AJAX Loop

I'm seeing this in Safari 7.1.6 (9537.85.15.3) on Mac.

To reproduce:

1) Create an account and login allowing Safari to save the password.
2) Change the password or recreate the account using the same email address with a different password.
3) Logout.
4) Add items to cart and checkout.
5) Enter the same email address in account information and focus on another field.

In my testing, I see the AJAX throbber and "Please wait..." message flashing over and and over as the AJAX hammers the server. As soon as Safari adds the stored password to the field, the AJAX is triggered. When it determines that the password is incorrect, it clears the password, starting the whole process over again.

There is no way to get out of the loop and revisiting the checkout page reproduces the same results. The only way I've been able to complete an order once this happens is to login before visiting checkout.