Stocks sputtered out of the starting gate Tuesday, posting losses in firm trading. The Dow Jones industrial average slipped 0.5% at the start of trade. The Nasdaq and the S&P 500 each dimmed 0.4%. Volume rose 31% on the Nasdaq and was 5% higher on the NYSE, compared with the same time Monday. The stock market today appeared to draw little strength from a healthy reading on U.S. trade in March.