IBM Third-Quarter Net Flat After Charge  NEW YORK (Reuters) - International Business Machines Corp.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=IBM.N target=/stocks/quickinfo/fullquote"&gt;IBM.N&lt;/A&gt; on Monday posted a flat quarterly net profit, weighed  down by the partial settlement of an employee pension lawsuit  and lackluster sales in its mainstay computer services  business.