Is it possible you're on a corporate network with an authenticated web proxy?
If so, please try from a non-proxied network. If this works then we can get you a list of URLs to be white-listed by your security team.
Thanks for the reply Bill. Yes, I am behind a corporate network with an authenticated web proxy. I will try at home tonight.
Bill, you were right. The lab loaded fine at home. Thank you for the help.