Success!

But not for the reason I mentioned below. Cleaning out the site, although a task that was desperately needed, didn't take care of the problem. So I turned to Blogger's troubleshooting section for help. Up until now, my blog settings had my ISP's FTP server name, pages.cthome.net, for the FTP path. Blogger Help suggested that I ping my FTP server and get the IP address and substitute the server name with the IP address in my blog's FTP settings. And it worked. Yay!

Why the server name no longer worked is beyond me. I'm just glad it's fixed.