This plugin worked fine with my sub-directory installation up until setting up the .htaccess file so the site's URL would hide that sub-dir.
So, I had to fix a few things in toptions.php
change line 22 to:
change line 42 to:
var checkurl='<?= $url2; ?>/check.php';
change line 234 to:
<tr><td colspan="4" align="center" class="first"><div id="loadingpic" style="width:128px;height:15px;background:url(<?= $url2;?>/load.gif);"> </div>