I just checked the access logs, you had a typo in your username, and you entered it in incorrectly (with an extra / in the end of URL instead of exactly as written on the site). The server (did what it was suppose to do when it sees that URL) sent you a blank file with no content, and so your installer had no packages downloaded from repo.sc.

I _WOULD_ (and trust me, I really want to because this feature is super-dooper-neat) offer a click-able link that will automatically add the repo for you so you don't need to worry about typo and stuff; but Installer is broken right now and not handling the http header correctly... As such, it doesn't work anymore (*cry*)...