After updating to a later kernel such as 2.6.32-26 or 2.6.32-27, grub may fail to boot with the following error:

"Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)"

Booting to earlier kernels boots successfully.

The update appears to have configured grub.cfg incorrectly without an initial ram drive.

After initial installation:

menuentry 'Ubuntu, with Linux 2.6.32-27-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod ext2
	set root='(hd0,4)'
	search --no-floppy --fs-uuid --set feeeee73-2049-4c21-bd73-13d72351bf52
	linux	/boot/vmlinuz-2.6.32-27-generic root=/dev/sda4 ro   quiet splash
}

To correct this, run the following command:

$ sudo update-grub
[sudo] password for user: 
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.32-27-generic
Found initrd image: /boot/initrd.img-2.6.32-27-generic
Found linux image: /boot/vmlinuz-2.6.32-25-generic
Found initrd image: /boot/initrd.img-2.6.32-25-generic
Found linux image: /boot/vmlinuz-2.6.32-24-generic
Found initrd image: /boot/initrd.img-2.6.32-24-generic
Found memtest86+ image: /boot/memtest86+.bin
done

The initial ram drive will now be present:

menuentry 'Ubuntu, with Linux 2.6.32-27-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod ext2
	set root='(hd0,4)'
	search --no-floppy --fs-uuid --set feeeee73-2049-4c21-bd73-13d72351bf52
	linux	/boot/vmlinuz-2.6.32-27-generic root=UUID=feeeee73-2049-4c21-bd73-13d72351bf52 ro   quiet splash
	initrd	/boot/initrd.img-2.6.32-27-generic
}