I get the error described in this thread, "500 - Passwords do not match. Please re-enter password."
I see this when i:
am not logged in,
add multiple items to the cart,
go to the registration page,
try to remove an item from the cart displayed below the login area.
The remove item link takes you to the error page.
I noticed that the browser automatically enters username and password, when this is not entered there will not be an error.
(I do not submit the password to get the error, I only try to remove an item from the cart)