Error with 'Language/Currency Links in Header'

I've installed the 'Language/Currency Links in Header' from Neville Kerr and it all works fine except when I try and view order details within the list of Orders in the Admin area.

I get the following message if I click on 'Edit' -

Fatal error: Cannot redeclare class currencies in /var/www/vhosts/3dministries.com/httpdocs/shop/includes/classes/currencies.php on line 102

Can anyone help please?

Thanks,

Andy

***please don't repost***