Thanks. That was a good idea. Problem solved.
Only it wasn't a Chrome extension, but an Opera one, "https everywhere." (That extension, though, is probably in the Chrome store too, but the Opera store carries it, and that's where I got it. I have that extension for both Firefox and Opera 23. So when I deactivated it in Opera 23, and in Firefox, the Fox Videos work in both browsers. Now I think that extension is useful, so I posted the problem on the Opera add-on website (for their extension). Hopefully, they'll get it working.