Missing a closing anchor tag (and you have a random extra one in there...):
Code:
<td align="left" valign="top">
<img src="$stylevar[imgdir_misc]/head_left.gif" alt=""/></a>
</td>
<td align="right" valign="bottom">
<a href="$vboptions[forumhome].php$session[sessionurl_q]">
<img src="$stylevar[imgdir_misc]/head_right.gif" border="0" alt="" />
</a>
</td>
Remove the red one and add the green one.