BuddyPress.org

I have also now tried resetting the permalinks, by using the save the option, and still no change.

I checked the .htaccess file against the default and nothing has changed, so the site has the default .htaccess settings, does it need any custom entries for Buddypress?

The BuddyPress install was manual, upload the BuddyPress folder to /wp-content/plugins/

Then moved the bp-default themes to /wp-content/themes/ and activated the theme

David