"Class 'Twig_Node_For' not found

Hi, just trying my first install of Grave but getting this error:

Whoops\Exception\ErrorException thrown with message "Class 'Twig_Node_For' not found"

you can see full details of the error here:
http://www.ninesevenseven.co.uk/grav-skeleton-woo-site/

Thanks for any help!