Hi there,
have just upgraded to the latest version of WP from 3.5.2 in my test environment before going live.
I had previously made some changes to the wp-login.php code for error messages following login, registration and lost password.
For some bizarre reason I can no longer see where any of the code is for the registration error messages in the wp-login.php e.g:-
ERROR: This username is already registered. Please choose another one.
ERROR: This email is already registered, please choose another one.
ERROR: Please type your e-mail address.
The error messages are still showing if a user enters a username or email already registered or forgets to enter an email address, so they are obviously somewhere, the question is where are they if they have been moved from wp-login.php
Kind regards