The NYSE's troubles didn't extend to the dozens of other exchanges that also trade U.S. stocks, such as the Nasdaq, so investors were still able to buy and sell stocks easily Wednesday.
The Dow Jones industrial average lost 261 points, or 1.5 percent, to 17,515.
The Standard & Poor's 500 gave up 34 points, or 1.7 percent, at 2,046 and the Nasdaq was down 87 points, or 1.8 percent, at 4,909.