The site popped for me here in the USA. 😉 I ran your site through GeoPeeker and saw the difference in load times depending on location -- with USA being the fastest. But it did show that the screen shots lagged quite a bit when all locations were trying to access.
Did you look at your YSlow score? The first 5 "F"s could directly impact users. Particularly a CDN. Maybe try resolving those issues and see if the situation improves?
Judith "Many of life's failures are people who did not realize how close they were to success when they gave up." ~Thomas Edison