Version 0.9, running on my windows test machine...
In wp-cache.php lines 946 onward. When wp-super-cache is reset to defaults or on first config, it creates a bad value in wp-cache-config.php:
define( 'WPCACHEHOME', WP_CONTENT_DIR . "E:/tech/wp/slty/wp-content/plugins/wp-super-cache/" );
Looks like the problem is line 947, creating a value for $dir that is not referenced to WP_CONTENT_DIR.
Workaround: hand-patch wp-cache-config.php