Index: wp-admin/user-new.php
===================================================================
--- wp-admin/user-new.php	(revision 22403)
+++ wp-admin/user-new.php	(working copy)
@@ -113,7 +113,6 @@
 	} else {
 		// Adding a new user to this blog
 		$user_details = wpmu_validate_user_signup( $_REQUEST[ 'user_login' ], $_REQUEST[ 'email' ] );
-		unset( $user_details[ 'errors' ]->errors[ 'user_email_used' ] );
 		if ( is_wp_error( $user_details[ 'errors' ] ) && !empty( $user_details[ 'errors' ]->errors ) ) {
 			$add_user_errors = $user_details[ 'errors' ];
 		} else {
Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 22403)
+++ wp-includes/ms-functions.php	(working copy)
@@ -490,9 +490,6 @@
 			$wpdb->delete( $wpdb->signups, array( 'user_login' => $user_name ) );
 		else
 			$errors->add('user_name', __('That username is currently reserved but may be available in a couple of days.'));
-
-		if ( $signup->active == 0 && $signup->user_email == $user_email )
-			$errors->add('user_email_used', __('username and email used'));
 	}
 
 	$signup = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->signups WHERE user_email = %s", $user_email) );