Display featured image as post thumbnail

Try this code.

Then temporarily set permissions to the cache folder to 774 and the timthumb.php file to 750, you can increase or decrease the permissions as you see fit (or aslong as it stops working, then it’ll be time to loosen up the permissions).

<?php
    // If there are images get them
    if ( $images = get_children(array(
        'post_type' => 'attachment',
        'numberposts' => 1,
        'post_status' => null,
        'post_parent' => $post->ID
    )));

    foreach( $images as $image ) {
         $attachment = wp_get_attachment_image_src( $image->ID );

    // Variables for timthumb
    $width = 160;
    $height = 160;
    $zoom_crop = 1;
?>

<a href="https://wordpress.stackexchange.com/questions/17411/<?php the_permalink() ?>" rel="bookmark" title="<?php esc_attr( printf( __( 'Click to read %s', 'truereps' ), get_the_title() ) ); ?>">
<img src="<?php bloginfo( 'template_directory' ); ?>/inc/scripts/timthumb.php?src=<?php echo $attachment[0]; ?>&amp;w=<?php echo $width; ?>&amp;h=<?php echo $height; ?>&amp;zc=<?php echo $zoom_crop; ?>" alt="<?php the_title(); ?>" />
</a>

<?php } ?>