I browsed to the your test site from a remote location that has never visited your site before and it does not use any proxy or whatever. Still the same problem.

 

I have cleared the cache of my browser, I have deleted the cache of the ISA Firewall, I have deleted the ISA Firewall cache and rebooted my server and laptop to be 100% sure. It does not work as it supposed to be. If you insert a link it shows sometimes nothing or it shows the URL instead of the text.