Oh, I'm well aware of the difference between HTTP and HTTPS. A lot of people don't realize that even something as big as Facebook has both a HTTP and an HTTPS connection available. Depending on what URL you use to access the site (this and most others), you get either a non-secure or a crypto-covered connection.
Sol's answer is probably the right one. It takes a while for a given URL to be propagated throughout the DNS servers. Until it is fully disseminated, you get security glitches if your browser is looking for a HTTPS and all it can find is HTTP.