WP-Performance-Gettext-Patch

In Cpanel and all seems OK, but I still get this error:

Cache directory is not writable. Please grant your server write permissions to the directory: /home/moretonb/public_html/wp-content/plugins/wp-performance-gettext-patch/wp-lang/

Also cannot find file—/wp-lang/
to change permissions.

http://wordpress.org/extend/plugins/wp-performance-gettext-patch/