Index: wp-admin/user-new.php
===================================================================
--- wp-admin/user-new.php	(revision 17521)
+++ wp-admin/user-new.php	(working copy)
@@ -31,7 +31,7 @@
 	add_filter( 'wpmu_signup_user_notification_email', 'admin_created_user_email' );
 
 	function admin_created_user_subject( $text ) {
-		return "[" . get_bloginfo('name') . "] Your site invite";
+		return sprintf( __( '[ %s ] Your site invite' ), get_bloginfo( 'name' ) );
 	}
 }