Well I'm an idiot - the fulltext index on page_text was missing from a default installation. It didn't break searches but probably slowed them down tremendously. Also set engine to MyISAM on page_text to avoid cryptic error messages from MySQL.
echo '<p>The administrator has flagged the page "' . $_SERVER['REQUEST_URI'] . '" so that it cannot be accessed from the web. Perhaps this is because this is a cache or includes directory and only needs to be accessed by scripts.</p><p>HTTP error: 403 Forbidden</p>';