here is what i did .. I found this in the file wp-config.php
/** Sets up WordPress vars and included files. */
require_once(ABSPATH . 'wp-settings.php');
then above the line:
require_once(ABSPATH . 'wp-settings.php');
I entered a new line:
define('WPCACHEHOME', dirname(__FILE__) . '/wp-content/plugins/wp-super-cache/');
so the final product looked like this:
/** Sets up WordPress vars and included files. */
define('WPCACHEHOME', dirname(__FILE__) . '/wp-content/plugins/wp-super-cache/');
require_once(ABSPATH . 'wp-settings.php');
hope this helps