Blue-Chip Stocks Dip, AIG Rises  NEW YORK (Reuters) - U.S. blue chips declined slightly  early Monday afternoon, with gains in insurance company  American International Group Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AIG.N target=/stocks/quickinfo/fullquote"&gt;AIG.N&lt;/A&gt;  and 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; offsetting a drop in energy stocks, which fell  along with crude oil prices.