At that point in the installation, the X-windows system is usually started and the "graphical" interface accessed. When it fails there, it's probably because the video driver is incorrect.
When I was installing FC6, I "bombed" there, because Fedora has no ATI drivers (nor any other proprietary drivers), and my screen size was non-standard. I used the "linux text" install option to do the installation in "text" mode, set up the YUM repositories to access livna and installed the "missing" video driver. Then, when I rebooted, all was well. (Except that the installer used the 586 kernel version instead of the 686 version, but that's another story.)