If it loads at all, this takes an age, usually, nil response
http://s7.addthis.com/js/250/addthis_widget.js?pub=fooo

If you access with https
https://s7.addthis.com/js/250/addthis_widget.js?pub=fooo

It works fast and fine

If you access with hidemyass.com or similar, no problem.

If you remove the pub= then sometimes it works, but it's always SLOW.

I can only assume at this point, that the proxy farm is most likely at fault.