ImClone Posts Profit on Erbitux Sales  CHICAGO (Reuters) - ImClone Systems Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=IMCL.O target=/stocks/quickinfo/fullquote"&gt;IMCL.O&lt;/A&gt; on  Thursday posted its third successive quarterly profit helped by  strong sales of its new colon cancer drug Erbitux.