Concerns about an impending currency war are being stoked again as leaders gather in South Korea for a meeting of the world’s top 20 economies.  At issue — the Federal Reserve's plan to pump 600 billion dollars of additional liquidity to jump-start the sluggish U.S. economy.  Some analysts say the U.S. plan will hurt emerging markets by driving other currencies higher, scuttling hopes for a multilateral agreement on many trade issues.  Mil Arcega reports.