Hi Kilrathy,
Please open wordpress-popular-posts.php using a code editor such as Windows’ Notepad or Adobe Dreamweaver, find this code:
<!-- WordPress Popular Posts v<?php echo $this->version; ?> -->
<script type="text/javascript" charset="utf-8">
/* <![CDATA[ */
//jQuery.post('<?php echo admin_url('admin-ajax.php'); ?>', {action: 'wpp_update', token: '<?php echo $nonce; ?>', id: <?php echo $id; ?>});
jQuery.post('<?php echo bloginfo( 'url' ); ?>/wp-admin/admin-ajax.php', {action: 'wpp_update', token: '<?php echo $nonce; ?>', id: <?php echo $id; ?>});
/* ]]> */
</script>
<!-- End WordPress Popular Posts v<?php echo $this->version; ?> -->
… and change it to:
<!-- WordPress Popular Posts v<?php echo $this->version; ?> -->
<script type="text/javascript" charset="utf-8">
/* <![CDATA[ */
//jQuery.post('<?php echo admin_url('admin-ajax.php'); ?>', {action: 'wpp_update', token: '<?php echo $nonce; ?>', id: <?php echo $id; ?>});
jQuery.post('<?php echo bloginfo( 'wpurl' ); ?>/wp-admin/admin-ajax.php', {action: 'wpp_update', token: '<?php echo $nonce; ?>', id: <?php echo $id; ?>});
/* ]]> */
</script>
<!-- End WordPress Popular Posts v<?php echo $this->version; ?> -->
Let me know if that fixes your problem, ok?