I have always put this in the template ad_footer_end which happens to be inserted right above the div at the end of the footer. Have you tried just using that hook? I'm not sure it will work, but:
PHP Code:
$ad_location['ad_footer_end'] .= your stuff;
Or, I think you can insert it right above the copyright, so do a str_replace on "<div id="footer_copyright"" and insert your code above it (or above the cron stuff right below the copyright).