Fix

This widget modifies the global variable $post, modifying the behavior of other widgets. I used this fixed function:

//Display the sidebar posts if there are any.
function get_post_to_sidebar_data(){
	global $post_to_sidebar;
	global $post;

	$post_bak = $post;

	if ($post_to_sidebar) {
		foreach ($post_to_sidebar as $post):
		setup_postdata($post);

		?>
		<div class="post-to-sidebar">

			<?php the_title('<h3 class="widget-title">', '</h3>'); ?>

				<div class="sidebar-entry-content">
					<?php the_content(); ?>
					<?php edit_post_link('Edit', ' | ', ' | '); ?>
				</div>
		</div>
		<?php
		endforeach;
		rewind_posts();

		$post = $post_bak;
		setup_postdata($post);

		?>
	<?php
	}
}

http://wordpress.org/extend/plugins/post-to-sidebar/