>>I used the current live build with non-free firmware.
Can you provide a link where you got this or did you build it yourself?
>>I can run orca on the running live system, but the boot menu is inaccessible.
How do you run the live system if the boot menu isn't accessible? It must just be timing out or something and booting straight into it.
>>I'm trying the live because I cannot get sound on the net install.
Have you got sound on the live system when it is running? If yes it's probably due to non-free firmware being available.