Database set correct, files in folder, but weird php error

Hi I’m about to start work on a new site called http://www.stepping-stones.org.uk and the site wont allow me to install? I’ve usually a good determination to resolve things like this but this one is beyond me.

There are a number of mysql servers on there already, but I created a fresh one and set up the wp-config manually.

I’ve successfully connected but it gives me a WSOD on install,
so I added some options in the wp-config:

define(‘WP_DEBUG’, true);
define(‘WP_MEMORY_LIMIT’, ’64M’);

here is what the debug gives me:

Warning: require_once(/home/sites/stepping-stones.org.uk/public_html/wp-includes/cache.php) [function.require-once]: failed to open stream: No such file or directory in /home/sites/stepping-stones.org.uk/public_html/wp-includes/load.php on line 412

Fatal error: require_once() [function.require]: Failed opening required ‘/home/sites/stepping-stones.org.uk/public_html/wp-includes/cache.php’ (include_path=’.:/usr/share/pear5:/usr/share/ZendFramework’) in /home/sites/stepping-stones.org.uk/public_html/wp-includes/load.php on line 412

can you shed any light on this?
http://www.stepping-stones.org.uk/wp-admin/install.php