Theme not working for anonymous users?

This is probably something that has been addressed before accept I can't find any post on it.

I've recently changed my Drupal Theme from Andreas02 to Garland and the theme doesn't work for 'anonymous users', i.e. users not logged in. Those people still see the Andreas02 theme? This has nothing to do with the admin theme as this is set to default.

There must be a file somewhere telling these pages to use Andreas as default? www.digitalschool.ie/digitalschool

Thanks for any help in advance.