It wasn't surprising that the market pulled back, having been pounded by months of losses and having driven the Dow Jones industrials up more than 470 points so far this week ahead of the late-day downturn.

Anthony Conroy, managing director and head trader for BNY ConvergEx Group, said expectations of more downgrades of bond insurers like Ambac Financial Group Inc. and MBIA Inc. — as well as uneasiness ahead of Thursday's Commerce Department report on personal income and spending inflation — was enough to spur people to cash in profits from the market's initial gains.

Key reports on the job market and manufacturing set to arrive Friday could also add to investors' concerns about the state of the economy, which has been dragged down by a crumbling housing market and losses at major financial institutions.

"Volatility is here to stay," Conroy said. "People who think these issues will go away overnight in one Fed rate cut are mistaken."

According to preliminary calculations, the Dow, which had been up more than 200 points after the Fed's decision, closed down 37.47, or 0.30 percent, at 12,442.83.