Viacom Posts a Loss on Charges  NEW YORK (Reuters) - Viacom Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=VIAb.N target=/stocks/quickinfo/fullquote"&gt;VIAb.N&lt;/A&gt;&lt;VIA.N&gt; on  Thursday posted a quarterly loss on charges related to the  spinoff of video rental chain Blockbuster Inc.&lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BBI.N target=/stocks/quickinfo/fullquote"&gt;BBI.N&lt;/A&gt;, but  cable network advertising sales and profits rose strongly.