OK, here's something really bizarre: the problem randomly fixed itself!
Just after I posted that comment, I closed my session (which had 3 tabs open) and started a new one, hoping to check the "restore previous session" option. Just then, I was directed to the NoScript home page, like it's supposed to do when you install NoScript, and I got the pop-up that's supposed to show up when you first install HTTPS Everywhere. Now, I get the homepage like I'm supposed to when Abrowser starts.
