Stocks Drop After Greenspan Testimony NEW YORK - Investors were unmoved by Federal Reserve Chairman Alan Greenspan's improved assessment of the economy, with stocks falling narrowly Wednesday in light trading.    While Greenspan said the economy has "regained some traction" after the summer's slowdown, he echoed Wall Street's concerns over energy prices, which have fallen from record highs in recent weeks but stubbornly remain above \$40 per barrel...