Index: wp-includes/registration.php
===================================================================
--- wp-includes/registration.php	(revision 6301)
+++ wp-includes/registration.php	(working copy)
@@ -97,7 +97,7 @@
 	if ( empty($user_registered) )
 		$user_registered = gmdate('Y-m-d H:i:s');
 
-	$data = compact( 'user_pass', 'user_email', 'user_url', 'user_nicename', 'display_name' );
+	$data = compact( 'user_pass', 'user_email', 'user_url', 'user_nicename', 'display_name', 'user_registered' );
 
 	if ( $update ) {
 		$wpdb->update( $wpdb->users, $data, compact( 'ID' ) );