Comment 153 for bug 396286

Performing the same test as above (removal of initrd.img and modification of GRUB's menu.lst) using 2.6.32-14-generic further confirms that the issue is with something that gets included in the initramfs image.

The relevant GRUB menu excerpt:

title Ubuntu lucid (development branch), kernel 2.6.32-14-generic
kernel /boot/vmlinuz-2.6.32-14-generic rootfstype=ext4 root=/dev/sda1 ro vga=795 quiet splash