The problem when publish a post

I have the plugin installed (HeadSpace2) but found today that when updating a custom post type, I get the following errors. These appear on the page after I click the update button, though the post does update.

This plugin is not setup for the post type either.

Warning: mb_strtolower() [function.mb-strtolower]: Unknown encoding "" in /home/admin/domains/xxxxx.net/public_html/wp-content/plugins/headspace2/modules/page/tags.php on line 136

Warning: Cannot modify header information - headers already sent by (output started at /home/admin/domains/xxxxx.net/public_html/wp-content/plugins/headspace2/modules/page/tags.php:136) in /home/admin/domains/xxxxx.net/public_html/wp-includes/pluggable.php on line 934