Issues browsing to specific site in IE from Windows 2003 Citrix server

I have a very strange issue and I hope someone can help.

Environment:

- Six servers
- All are Windows 2008 R2 except for our two XenApp servers which are Windows 2003 R2
- Two DNS servers that are forwarding to OpenDNS for malware filtering only
- Citrix XenApp Fundamentals on the two Windows 2003 R2 servers


Issue:

When a user (or an admin) tries to browse to http://www.grantsolutions.gov from Internet Explorer on either Citrix server, they get a "Page Cannot be Displayed" message. All other servers on the network can get to the site successfully.


Steps Taken:

- Tested from Firefox, it works without issue.
- Tested from Google Chrome, the page fails to load, but I recieve an error regarding the site's SSL Intermediate certificate and hostname certificate.
- Manually installed all the certs from Entrust.net (the site's SSL authorative)
- Tested ping, nslookup, telnet and tracert. All succeed without issue.
- Cleared all DNS cache
- Reset IE browser, added site to safe sites, disabled pop-up blocker... etc.
- Tested in IE with add-ons disabled
- Ran a malware scan and verified that the hosts file was not corrupt
- Checked the Winsock, no issues found
- Tested on another client's Windows 2008 R2 server running Citrix XenApp, I was able to browse successfully in IE
- Tested on another client's Windows 2003 R2 server running Citrix XenApp and the site failed with a "Page Cannot be Displayed" error
- Verified that other HTTPS websites open successfully on both Citrix servers


Investigation Outcome:

I believe that the problem possibly lies with the website's SSL certificate and how Windows 2003 handles trusted root certs with Citrix installed. Unfortunately, I'm at a loss as to what EXACTLY is the cause.


Any help would be appreciated!


Thanks,

Adam