If it's from an unrelated part of the site, then it shouldn't be getting triggered when going to the showthread page. It wouldn't hurt to disable your plugins and see if that stops the errors.
Note: To temporarily disable the plugin system, edit config.php and add this line right under <?php
PHP Code:
define('DISABLE_HOOKS', true);
Is there anything in your error_logs? And what about this hiccup you say vb had - what was that all about?