Entypo Fontello not showing in Mozilla with forwarded secondary domain

Hi there.
I have a site that utilises 2 domain names. The secondary URL is based in Bhutan, http://www.btb.com.bt and points to the server that the site is hosted on in the U.S., and when viewing the site using this domain name on Mozilla the icons are all missing. This is occuring on both MAC and PC. It appears to be fine on Safari. I think it is due to the font being served from a different domain, as I believe that Firefox requires that all font assets be served from the same domain. Everything appears fine when viewed via the primary domain http://www.bhutantravelbureau.com.
Is there something I can add to CSS of htaccess to force the display of this font?

By the way I know this is off topic but I achieved excellent site download speeds using WP Super Cache, Autoptimise and Smush.it. Hosted with godaddy, I was having massive issues with a 60% loading ranking. It is now up to 90%. I know this is a big issue with a lot of users, and you probably already know this, but just wanted to share my experience.

Cheers