HTML emails still lack the features that browsers makeup for on websites, it's like developer in HTML for IE 5. The anchor tag will not work around tables and sometimes will not even work around divs, however obviously webpages do not have these problems. This is due to the standards not really being recognised by mail clients as they are in browsers.
Try wrapping the content in the cells in just the anchor tag, around your button:
<table border="0" cellpadding="9" width="100%" align="center" cellspacing="0" class="templateButton displayinline" mc:hideable>
<tr>
<td align="center" valign="middle" class="templateButtonContent">
<a href="#" target="_blank">Sony</a>
</td>
</tr>
</table>
I know it's not ideal, however it is a way around this problem.