Custom post type issues

<?php $loop = new WP_Query( array( 'post_type' => 'case_studies', 'posts_per_page' => 10 ) ); ?>

<?php while ( $loop->have_posts() ) : $loop->the_post(); ?>

    <article>

        <h2><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Continue reading about %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark"><?php the_title(); ?></a></h2>

        <?php // set the title for the post thumbnail image
                $default_attr = array(
                                    'title' => trim(strip_tags( $attachment->post_title )),
                                    );

            if(has_post_thumbnail()) { ?>


                <a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Continue reading about %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ); ?>" class="post-thumnail">
                    <?php the_post_thumbnail( array( 210, 140, true ), $default_attr); ?>
                </a>
        <?php } ?>

        <?php the_excerpt(); ?>

        <p><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Continue reading about %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark"><?php printf( esc_attr__( 'Read more about %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ); ?></a></p>


    </article>
    <?php endwhile; ?>

    <?php rewind_posts(); wp_reset_query(); ?>

    </section>

    <section id="sidebar">
    <?php get_sidebar(); ?>
    </section>