This is an issue with the e-commerce plugin it loads on all custom post types and it shouldn’t; specially when other plugin are making ajax calls. We have recently helped a customer with this issue.
Add this code in the functions.php file of your theme or create a plugin.
function ims_fix_issue_wp_ecommerce( $filepath ){
remove_filter('wp_insert_post_data','wpsc_pre_update', 99, 2 );
remove_action( 'save_post', 'wpsc_admin_submit_product', 10, 2 );
return $filepath;
} add_action( 'ims_before_read_image', 'ims_fix_issue_wp_ecommerce');