Can't boot after I did a aptitude full-upgrade and let it update menu.lst (did a diff first and it looked good).

This is what I've done so far in the BusyBox shell:

mkdir /tmp/xvda1
mount /dev/xvda1 /tmp/xvda1
chroot /dev/xvda1
nano /boot/grub/menu.lst

This file looks like this:

title           Ubuntu 12.04.1 LTS, kernel 3.2.0-31-virtual
root(hd0,0)
kernel          /boot/vmlinuz-3.2.0-31-virtual root=UUID=/dev/xvda1 ro quiet splash
initrd          /boot/initrd.img-3.2.0-31-virtual

title           Ubuntu 12.04.1 LTS, kernel 3.2.0-31-virtual (recovery mode)
root(hd0,0)
kernel          /boot/vmlinuz-3.2.0-31-virtual root=UUID=/dev/xvda1 ro  single
initrd          /boot/initrd.img-3.2.0-31-virtual

titleUbuntu 12.04.1 LTS, kernel 3.2.0-24-virtual
root(hd0,0)
kernel/boot/vmlinuz-3.2.0-24-virtual root=UUID=/dev/xvda1 ro quiet splash
initrd/boot/initrd.img-3.2.0-24-virtual

titleUbuntu 12.04.1 LTS, kernel 3.2.0-24-virtual (recovery mode)
root(hd0,0)
kernel/boot/vmlinuz-3.2.0-24-virtual root=UUID=/dev/xvda1 ro  single
initrd/boot/initrd.img-3.2.0-24-virtual

titleUbuntu 12.04.1 LTS, kernel 3.2.0-24-generic
root(hd0,0)
kernel/boot/vmlinuz-3.2.0-24-generic root=UUID=/dev/xvda1 ro quiet splash
initrd/boot/initrd.img-3.2.0-24-generic

titleUbuntu 12.04.1 LTS, kernel 3.2.0-24-generic (recovery mode)
root(hd0,0)
kernel/boot/vmlinuz-3.2.0-24-generic root=UUID=/dev/xvda1 ro  single
initrd/boot/initrd.img-3.2.0-24-generic

titleChainload into GRUB 2
root(hd0,0)
kernel/boot/grub/core.img

titleUbuntu 12.04.1 LTS, memtest86+
root(hd0,0)
kernel/boot/memtest86+.bin

From what I remember, the upgrade added the UUID= string. Should I remove these? Or rather, how do I get my system back online again? Thanks.

Update: Seems like I can't even edit the file.

[ Error writing /boot/grub/menu.lst: Read-only file system ]