Updated from 4:16 p.m. ESTMajor stock averages gave up their gains in the last hour of trading Thursday, as better-than-expected economic data couldn't keep blue chips and tech shares from closing near the flat line. The Dow Jones Industrial Average tacked on 12.76 points, or 0.1%, to 13,056.72. For a second straight session, Intel ( INTC) was the weakest component on the Dow, falling 2.7%. The S&P 500 was unchanged at 1447.16. The Nasdaq Composite was the weakest performer, fluctuating between positive and negative territory all day before ending down 6.95 points, or 0.27%, at 2602.68. Helping the Dow and S&P advance early was the ADP report on employment, which said private payrolls exceeded forecasts with a rise of 40,000 in December. Despite the report's short history and somewhat spotty record, traders viewed it as positive ahead of the government's own nonfarm payrolls numbers, due Friday. But by the late afternoon, investors grew a bit jittery ahead of the Labor Department report, and the momentum faded. "It's disturbing we couldn't retrace much of yesterday's decline," said Art Hogan, chief market analyst with Jefferies. "There's a lot of nervousness over tomorrow's nonfarm payrolls number. If we do get a downside surprise, that number combined with the weak manufacturing data we got yesterday will show a slowing economy and will not be good for stocks going forward."