This is a bit outdated but I stumbled on this forum when I had this same problem with my root password. It was driving me crazy because I had just done a restore and I could not figure out why my password was not working. I found the solution though and I hope it helps others because I looked everywhere and I tried every password I have ever used for anything. Anyway, I use ifunbox for my SSH needs, I am assuming as part of the ifunbox procedures it resets your password or something else did; but open ifunbox, go to help -> troubleshoot ->show openSSH password. Voila. I used that incredibly long alphanumeric number it showed and it worked like a charm. Then I could run the passwd step to change the password to something I could remember