Goldman Cuts Wal-Mart Rating  NEW YORK (Reuters) - Wal-Mart Stores Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WMT.N target=/stocks/quickinfo/fullquote"&gt;WMT.N&lt;/A&gt;, the  world's biggest retailer, suffered another blow to its star  status on Wednesday when a leading U.S. investment bank  downgraded the company's stock.