Sounds more like a DNS problem. Glad it's resolved. In future, you might want to try and "ping" the website, even if you don't get a reply, you can see if it resolves the DNS name as it will report the IPadress it has resolved from the name. If it reports "could not find host" then it's possibly a DNS issue, and squid cache has no effect. Perhaps even an ipconfig /flushdns from the client computer is all that is needed.