this plugin is building a XML file with information about images in all the posts.
The problem is that when you have a large amount of posts, this plugin just runs out of memory:
$posts = $wpdb->get_results("SELECT post_content, post_title FROM $wpdb->posts where post_status='publish'");
Then you are not able to save posts properly.
There should be a WP cron which would scan only up to 1000 posts in a single step.