Description of problem: Boot from rescue CD, choose HTTP install, but supply a URL that doesn't contain a .discinfo file (like, http://download.fedora.redhat.com/pub/fedora/linux/core/development/i386/os/Fedora instead of just .../os). The loader will then say it found local install media, but after the partition setup, will fail to find the repodata under the URL you gave it, and throw a fatal Abort. So probably the check for .discinfo is just looking in the wrong place. Experienced with rawhide rescue cd, haven't checked FC6.
This seems easy and reasonable, so I added it to loader. Try to pull .discinfo if we are going to load the second stage from the rescue CD. If it fails, send you back to the URL entry screen.