If that hadn't been it, the other thing I would have suggested, and is probably worth remembering for the future, is whether your browsers are set up to verify revocation of SSL certificates. That often fails, and without giving you any clues as to what's going wrong.
Thanks for that additional tip. I just checked and I don't see anything set up to check for revocations. In this case it was going to the URL and I could see the padlock at the bottom right. So it was navigating there but couldn't finish downloading the page. In reading through the URL that Rob sent me plus his explanation, the behaviour was consistent with what one would expect for such a problem (dropped packets). Thanks, Jacques B.