I am still having this same issue after upgrading to 9.2. I have reset the password locally through the menu. I go directly to the GUI and set the new password. I can then view the GUI and its menus. After I reboot though, I no longer have access to the GUI. It keeps saying that my password is incorrect for 'root'. I have done this sequence 3 times now with the same outcome. What's my next step?
edit: I seem to maybe remember that prior to the upgrade I had set the root user to be disallowed from logging in. I am not home so I can not reset the password again to gain access to the GUI, is that an option within the GUI to disallow root login? Is my solution as simple as resetting the password again and changing that setting within root's user profile?