Ok I just cut and pasted your code into both UBB.Threads 7.5.9 and UBB.Threads 7.6.0 with the only change of the actual image file name as follows below and it worked on both versions. I wanted to make sure that where I was testing it that it wasn't making a difference on the version of the UBB Software.

Code
<table class="t_inner" align="center" width="800">
<tr>
<td align="center" valign="middle" width="325">
<a href="http://YOUR_FORUM_URL/" target="_top">
<img src="{$config.BASE_URL}/images/{$style_array.general}/newpm.gif" border="0" alt="FORUM NAME" width="500" height="100"></a>
</td>
<td align="center" valign="middle">

<!--// This gives you another column for ads, etc //-->

</td>
</tr>
</table>