SEC Probes Bank of New York Clearing Unit  NEW YORK (Reuters) - Bank of New York Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BK.N target=/stocks/quickinfo/fullquote"&gt;BK.N&lt;/A&gt; on Tuesday  said regulators are examining whether its Pershing LLC unit  cleared improper stock trades.