My web host helped me out with this. They said that by default PHP shows an empty white screen when there is a PHP error. It is a security feature. If you can view the error log on your server, you might be able to decipher the message it gives you. In my case, it was the fact that not all the files had uploaded to the web host properly. I re-uploaded everything, and then the installation completed….I think, anyway. Because now I’m having a different problem – with uploading media.