Sears Posts Loss, Cuts Outlook Stock Down  NEW YORK (Reuters) - Sears, Roebuck   Co &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=S.N target=/stocks/quickinfo/fullquote"&gt;S.N&lt;/A&gt;, the largest  U.S. department store chain, on Thursday posted an unexpected  third-quarter loss and cut its full-year profit forecast,  sending its shares tumbling more than 8 percent.