üye olurken böyle bir hata veriyor

Warning: mysql_insert_id() [function.mysql-insert-id]: A link to the server could not be established in /home/.beeswax/sadasd/asda.com/modules/mod_register.php on line 46
Sorry, but there is a problem with our scripts!
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LIMIT 1' at line 1
UPDATE members SET highest_rank=2015 WHERE id= LIMIT 1


mod_register.php: 33. satırdan itibaren.

if ( isset( $error ) )
		$message = "<strong>Error</strong>: ".$error;
	else
	{
		$username = trim(stripslashes($_POST["username"]));
		$password = stripslashes($_POST["password"]);
		$email = strtolower(trim(stripslashes($_POST["email"])));
		$username = preg_replace("/\s{2,}/", ' ', $username);
		$db->query( "INSERT INTO members ( username, password, email, ".
					"joined, last_updated ) VALUES ( '".
					$db->escape( $username )."', '".md5($password)."', '".
					$db->escape( $email )."', UNIX_TIMESTAMP(), UNIX_TIMESTAMP() )" );
		$insert_id = mysql_insert_id();
		$db->query( "SELECT * FROM members" );
		$rank = $db->countRows();
	$db->query( "UPDATE members SET highest_rank=".$rank." WHERE id=".$insert_id." LIMIT 1" );
		$db->query( "UPDATE sessions SET member_id=".$insert_id.", admin='0' WHERE id='".
					session_id()."' LIMIT 1" );
		$ref = htmlentities( stripslashes( $_POST["ref"] ) );
		$ref = empty( $ref )? "/" : $ref;
		?>

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