The New York Stock Exchange was down on Wednesday due to a possible "configuration problem" with a software update, but trading still occurred at other venues.
Stocks fluctuated, with the Standard & Poors 500 Index near a record, amid corporate deals activity and data that showed retail sales rose less than forecast in April.
More than $41 billion has returned to U.S. exchange-traded funds that own shares in the past four weeks, reversing withdrawals that swelled to as much as $40.2 billion last month.