Nasdaq is back in business after an apparent technical glitch brought the exchange to a rare halt this afternoon for more than three hours, reports the Wall Street Journal. The exchange hasn't fully explained what happened, but trading of all Nasdaq securities ground to a halt just after noon today, reports MarketWatch. Other exchanges quickly suspended trading of Nasdaq stocks. "All orders in those securities have been canceled back to customers," says the New York Stock Exchange in a statement. Nasdaq blamed "quote submissions" in an email to investors.