METALS-Copper slips from 2-wk high after Bernanke speaks Wed Feb 29, 2012 2:22pm EST * Bearish Fed comments erode early copper rally * Copper prices post 2nd straight monthly gain * U.S. 4th quarter economic growth revised up * Coming up: Chinese manufacturing PMI Thursday By Chris Kelly and Harpreet Bhal NEW YORK/LONDON, Feb 29…