When booting from the latest USB Live, Raring amd64 on EFI (13-03-08), I get "an error occured while mounting /sys/firmware/efi/efivars".

If I ignore this message, the system reaches Unity, I'm able to proceed with an EFI install which completes without any errors, but upon rebooting the machine, it hangs on boot.

Any idea why I get this error from the USB Live?