Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 20327)
+++ wp-includes/ms-functions.php	(working copy)
@@ -445,7 +445,7 @@
 	$user_email = sanitize_email( $user_email );
 
 	if ( empty( $user_name ) )
-	   	$errors->add('user_name', __('Please enter a username'));
+	   	$errors->add('user_name', __( 'Please enter a username.' ) );
 
 	$illegal_names = get_site_option( 'illegal_names' );
 	if ( is_array( $illegal_names ) == false ) {
@@ -453,13 +453,13 @@
 		add_site_option( 'illegal_names', $illegal_names );
 	}
 	if ( in_array( $user_name, $illegal_names ) == true )
-		$errors->add('user_name',  __('That username is not allowed'));
+		$errors->add('user_name',  __( 'That username is not allowed.' ) );
 
 	if ( is_email_address_unsafe( $user_email ) )
 		$errors->add('user_email',  __('You cannot use that email address to signup. We are having problems with them blocking some of our email. Please use another email provider.'));
 
 	if ( strlen( $user_name ) < 4 )
-		$errors->add('user_name',  __('Username must be at least 4 characters'));
+		$errors->add('user_name',  __( 'Username must be at least 4 characters.' ) );
 
 	if ( strpos( ' ' . $user_name, '_' ) != false )
 		$errors->add( 'user_name', __( 'Sorry, usernames may not contain the character &#8220;_&#8221;!' ) );
@@ -471,7 +471,7 @@
 		$errors->add('user_name', __('Sorry, usernames must have letters too!'));
 
 	if ( !is_email( $user_email ) )
-		$errors->add('user_email', __('Please enter a correct email address'));
+		$errors->add('user_email', __( 'Please enter a correct email address.' ) );
 
 	$limited_email_domains = get_site_option( 'limited_email_domains' );
 	if ( is_array( $limited_email_domains ) && empty( $limited_email_domains ) == false ) {