I have come across an problem I have never seen before in linux.  I am not sure when it happened, but I am no longer able to log into my system under any name.  root, admin, or any user....  At the user prompt, I type either admin, root, or whatever, and the screen refreshes immediately, and does not even prompt me for a password....  Even a little more strange, I am able to log in over the internet (on a local machine) using admin and able to get to all of the interface.  I cannot get in as root - I have not set up ssh yet.  Any ideas on the not being able to log in to the machine itself?
Thanks