cloned drive doesn't boot up

[mucho]

I'm registered SD user, and recently having trouble with
backup OSX 10.4.2 from iBook G4 internal HDD to Firewire HDD.

I tried to duplicate internal HDD to external Firewire HDD
with plain setting, and it seems successful to clone the
contents of HDD (when I boot from internal HDD, external
HDD have whole contents that should be there). But once
I boot my iBook from the external HDD, glay apple icon in
boot-up screen soon changes into slash-in-circle icon and
boot-up sequence stops (while the circular animation below
is continuing to animate).

I've got no trouble when I clone 10.3.x in same setting so
I think hardware-related trouble doesn't concern. Would
you give me some advice about my trouble?