ERROR with get_posts within meta_box

I just developed a plugig that adds a Meta Box to a custom post type with some checkboxs (that are other custom post types, the title is the label of the checkbox).

I query the posts like this:

<?php
global $post;
$tmp_post = $post;
$args = array( 'post_type' => 'evento', 'posts_per_page' => -1, 'order' => 'ASC');
$myposts = get_posts( $args );
foreach( $myposts as $post ) :	setup_postdata($post); ?>
<input type="checkbox" class="event-day" name="<?php the_ID(); ?>" id="<?php the_ID(); ?>" /><?php echo get_the_translated_date (get_different_type_facts(get_the_ID(), 'heading'), 'j F'); ?><br />
<?php endforeach; ?>
<?php $post = $tmp_post;?>

And locally there is no problem, but with the website on the server, at every update or creation of the post I get these errors:

Warning: array_map() [function.array-map]: Argument #2 should be an array in /home/content/83/8177083/html/wp-includes/post.php on line 1684

Warning: Cannot modify header information – headers already sent by (output started at …/html/wp-includes/post.php:1684) in …/html/wp-includes/pluggable.php on line 934

What could it be??

THANKS!