This is with unmodified GENERIC, so INSECURE should be present - as I said, the same live USB system works fine with the Quadro 600 card on the desktop. I know about userconf, but I chose to place several test and spare kernels in / and modify boot.cfg accordingly.
Are you building without options INSECURE? (config -x)
You can also add 'userconf disable nouveau*' to boot.cfg to achieve the
same, without needing a custom kernel.