gene i can understand your pain. one of the reasons that i don't necessarily
like sudo systems.
one of the first things that i do when i have a sudo system, ubuntu, lmde,
raspbian, is to 'sudo su' and then 'passwd' to actually set a root password.
i have found that this has remedied the situation that you have described here.
with doing the above you wouldn't have to mount the sd somewhere else, you
just make a new password for root.
i hope that this helps some for future reference.