Membership.CreateUser without a security question

I'm trying to use the Membership.CreateUser method without passing a security question and answer. I set them to string.empty, but no go. I have my provider set to not require a question in my web.config. What am I doing wrong?
 
Dim newUser As MembershipUser = Membership.CreateUser(txtUserName.Text, txtPassword.Text, strEmail, String.Empty, String.Empty, True, result) ...