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might be different, but the administration from my user, when it asks for a
password it is looking for my user's password, not root's. My bet is, you
just forgot what root's password is, because it is used so infrequently (in
fact, Ubuntu doesn't give a known password to root after the default
install). Give this a try before you get too deep into thinking it is a
configuration problem.

I hope this helps,

Michael