viewothreads.php in admin
tdheader is wrong and the instructions need to be in a row for the style sheet.
In the 'Send them a page' section change this:
Place a checkmark by any threads you wish to close.
to this:
<tr><td colspan=4 class="lighttable">
Place a checkmark by any threads you wish to close.
</td></tr>
In the 'Send them a page' section change this:
<tr class="tdheader"><td>Close</td>
<td>Subject</td>
<td>Posted by</td>
<td>Posted on</td></tr>
to this:
<tr><td class="tdheader">Close</td>
<td class="tdheader">Subject</td>
<td class="tdheader">Posted by</td>
<td class="tdheader">Posted on</td></tr>