U.S. Blue Chips Flat After Data  NEW YORK (Reuters) - U.S. blue chips were flat on Monday  after a report showing an unexpected drop in November  construction spending offset a drop in oil prices, while a  brokerage downgrade of Sun Microsystems &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=SUNW.O target=/stocks/quickinfo/fullquote"&gt;SUNW.O&lt;/A&gt; hurt Nasdaq.