Zoroastro resolveu seu problema? Porque você estava adicionando o caracter # no local errado, para exemplificar vou listar meu menu.lst. Para diminuir vou excluir as linhas com os comentários.
gfxmenu /boot/grub/message.ubugrey
default 0
timeout 10
color cyan/blue white/blue
title Ubuntu, kernel 2.6.17-11-generic
root (hd0,5)
kernel /boot/vmlinuz-2.6.17-11-generic root=/dev/hda6 ro quiet splash locale=pt_BR
initrd /boot/initrd.img-2.6.17-11-generic
quiet
savedefault
boot
title Ubuntu, kernel 2.6.17-11-generic (recovery mode)
root (hd0,5)
kernel /boot/vmlinuz-2.6.17-11-generic root=/dev/hda6 ro single
initrd /boot/initrd.img-2.6.17-11-generic
boot
#title Ubuntu, kernel 2.6.17-10-generic
#root (hd0,5)
#kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda6 ro quiet splash locale=pt_BR
#initrd /boot/initrd.img-2.6.17-10-generic
#quiet
#savedefault
#boot
#title Ubuntu, kernel 2.6.17-10-generic (recovery mode)
#root (hd0,5)
#kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda6 ro single
#initrd /boot/initrd.img-2.6.17-10-generic
#boot
title Ubuntu, memtest86+
root (hd0,5)
kernel /boot/memtest86+.bin
quiet
boot
### END DEBIAN AUTOMAGIC KERNELS LIST
# This is a divider, added to separate the menu items below from the Debian
# ones.
title Other operating systems:
root
# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/hda2
title Microsoft Windows XP Professional
root (hd0,1)
savedefault
makeactive
chainloader +1