Single external website extremely slow on internal network (via internet)

We are having an issue with a specific website that some of our users access for business purposes.

The website has become very slow and unresponsive since the past two weeks. We have Websense integrated with our ASA 5520 appliance for internet filtering.

This is the only website we are experiencing issues with. Symptoms include webpage timeouts, slow browsing between pages, very slow downloads ( a 1Mb PDF will take 5-10 minutes to download). Our internet connection is not the issue as every other website is fast.

I noticed through various troubleshooting this problem only occurs on our network. When I hit the website from an alternate network (home, DMZ,) it responds quickly. As soon as we try from our internal network, it is slow like molasses.

We tried turning off Websense web filtering, network agent, put an except rule in the firewall to allow all traffic to the website IP range through, as well as the source client IP.

We also looked at our ASA configuration lines pertaining to the websense filtering.

The following config is present:

url-block block 32
url-mempool 10240
protocol tcp version 4 connections 60

These parameters were implemented a while back to solve other issues we were having.

One odd thing I noticed is when pinging the website from our internal network, I am receiving 10-15% packet loss. From an external network, hardly any packet loss. Again this is specific to this one website, everything else is fine.

Any ideas?

The website in question is www.orbit.com