The GRUB bootloader is the preferred way of booting gNewSense after installation. During the installation the gNewSense installer will ask you two questions about GRUB. First, it wants you to define a Linux command line. Type in the following line in the box
console=tty no_auto_cmd machtype=8.9
Next the installer will ask you about the default Linux command line. The box will problably already have the value 'quiet' in it so you can just continue, but if it doesn't, make sure to write
quiet
... in the box.