At the boot help screens, the bottom line says you can press ENTER to boot, but it gives the error message, "No DEFAULT or UI configuration directive found!" I tried adding the syslinux option, "default" at the beginning of the kernel line in live.cfg, but then I got an error saying, "Could not find kernel image: kernel." Then I tried replacing the word "kernel" with "default" in the kernel line, so that the next thing in the line is the path to the kernel (/live/vmlinuz), and that resulted in a kernel panic (Unable to mount root fs on unknown-block).
I've looked at man syslinux a few times, and it's not clear where the word "default" is supposed to go. If someone knows, please tell me. Other option is to change the bottom line of instructions, so it says to do something that will work. (e.g. "- type 'live' and press ENTER to boot the default configuration")