Setting-Writting

Does anybody know why this will happen when I save the remote publishing option under setting-writting.

This is what i get:

Warning: Cannot modify header information – headers already sent by (output started at /home/antitalk/public_html/wp-content/plugins/post-slideshow-gallery/main.php:1) in /home/antitalk/public_html/wp-includes/pluggable.php on line 881