Josh,
I run beta4 on my test site. This hack works fine. Your template is a bit whacked from a stock template. Here is where it needs to be. Add everything between the $tbclose and $tbopen
<!-- END CATEGORY LOOP -->
<!-- END OF FORUM LOOP -->
$tbclose
<br />
UBBTPRINT;
require ("/usr/local/blah/blah/blah/templates/default/ubbt_photopost.tmpl");
echo <<<UBBTPRINT
<br />
$tbopen
Also did you fill out the photopost.inc.php file with your settings and upload it to your threads directory?