Posts Sitemap Fails

I have 85 posts on the site http://claystudiotour.com, for example: http://claystudiotour.com/judy-nelson-moore each of which has a wordpress gallery as the first item in the post with easyfancybox displaying the images in the gallery when clicked. The WordPress SEO sitemap for posts fails with this message: Fatal Error: Maximum execution time of 60 seconds exceeded in
/home/claystud/public_html/wp-includes/class-wp-image-editor-imagick.php on line 327

The same thing happens no matter what I set the maximum executive time to…set it for 300 seconds and it still didn’t work.

Why would the sitemap be calling the class-wp-image-editor-imagick.php at all? How can I get away from this and create a valid posts sitemap??

http://wordpress.org/plugins/wordpress-seo/