bootable clone on external drive won't recognize password

I used Super Duper to create a bootable clone on an external firewire drive.
When I restart my MBP holding down the option key I can choose the external drive. OSX (104.11) starts to load and then encounters a name and password popup. Entering the administrator name and password of the original drive fails. Only one account on the machine - still using the admin password originally chosen. Any thoughts, wise ones, as to why the clone won't recognize the password - or work arounds to allow this drive to boot?
Many thanks (first-time poster, long-time lurker).

 

No - standard admin password request

top line: Name___________
bottom line: Password__________

I never set up a firmware password - just the admin login and pw

 

no luck

I can change the pw on the MBP's HD - but I still run into a pw problem
when attempting to boot from the external drive. It's as if the clone had a different account name or password - which makes no sense, since it was
made with "copy all" from the internal drive. Thanks for bearing with me.