Squid/Squidguard will stall on certain websites

[pneumatic]

http://west.thomson.com

This website will not load (or take an extremely long time) through my pfsense installation (squid/squidguard - transparent no auth).  I am currently getting around this by loading the https version of the page but it would be nice to know why a small handful of sites do this.

Any help would be appreciated.