genesis_save_custom_fields function for saving meta box data http://wpsites.net/web-design/hand-coded-meta-box-for-genesis/

genesis-lib-functions-options.php

/**
 * Save post meta / custom field data for a post or page.
 *
 * It verifies the nonce, then checks we're not doing autosave, ajax or a future post request. It then checks the
 * current user's permissions, before finally* either updating the post meta, or deleting the field if the value was not
 * truthy.
 *
 * By passing an array of fields => values from the same metabox (and therefore same nonce) into the $data argument,
 * repeated checks against the nonce, request and permissions are avoided.
 *
 * @since 1.9.0
 *
 * @param array    $data         Key/Value pairs of data to save in '_field_name' => 'value' format.
 * @param string   $nonce_action Nonce action for use with wp_verify_nonce().
 * @param string   $nonce_name   Name of the nonce to check for permissions.
 * @param WP_Post|integer $post  Post object or ID.
 * @param integer  $deprecated   Deprecated (formerly accepted a post ID).
 *
 * @return mixed Return null if permissions incorrect, doing autosave, ajax or future post, false if update or delete
 *               failed, and true on success.
 */
function genesis_save_custom_fields( array $data, $nonce_action, $nonce_name, $post, $deprecated = null ) {

	if ( ! empty( $deprecated ) ) {
		_deprecated_argument( __FUNCTION__, '2.0.0' );
	}

	//* Verify the nonce
	if ( ! isset( $_POST[ $nonce_name ] ) || ! wp_verify_nonce( $_POST[ $nonce_name ], $nonce_action ) )
		return;

	//* Don't try to save the data under autosave, ajax, or future post.
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
		return;
	if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
		return;
	if ( defined( 'DOING_CRON' ) && DOING_CRON )
		return;

	//* Grab the post object
	if ( ! is_null( $deprecated ) )
		$post = get_post( $deprecated );
	else
		$post = get_post( $post );

	//* Don't save if WP is creating a revision (same as DOING_AUTOSAVE?)
	if ( 'revision' === get_post_type( $post ) )
		return;

	//* Check that the user is allowed to edit the post
	if ( ! current_user_can( 'edit_post', $post->ID ) )
		return;

	//* Cycle through $data, insert value or delete field
	foreach ( (array) $data as $field => $value ) {
		//* Save $value, or delete if the $value is empty
		if ( $value )
			update_post_meta( $post->ID, $field, $value );
		else
			delete_post_meta( $post->ID, $field );
	}

}