So, I ended up in a menu which allowed me to test the bootable USB stick I was trying to use to install 13.04 AMD server, and it reported errors. I downloaded another copy of the 13.04 ISO and made another bootable USB. This one allowed the system to be installed with no problems whatsoever, so maybe my problem was just a bad bootable image. I created the first one with Startup Disk Creator on 12.04 Desktop, and made the second bootable USB using the Pen Drive USB installer on Windows XP.
So, I ended up in a menu which allowed me to test the bootable USB stick I was trying to use to install 13.04 AMD server, and it reported errors. I downloaded another copy of the 13.04 ISO and made another bootable USB. This one allowed the system to be installed with no problems whatsoever, so maybe my problem was just a bad bootable image. I created the first one with Startup Disk Creator on 12.04 Desktop, and made the second bootable USB using the Pen Drive USB installer on Windows XP.