Bugreport by al Sten-Clanton:

interactive + lilo + ext3: works
interactive + grub + ext3: works
non-interactive + lilo + ext4: works
non-interactive + grub + ext4: does not work
non-interactive + grub + ext3: does not work

Note by mika: ext4 is not yet supported, though it's on my todo-/wishlist. Why 
installation of grub fails in non-interactive mode has to be debugged.