I've installed the "Lubuntu Desktop environment" from the Ubuntu Software Center, and then rebooted. The new interface asked for a username and password, but apparently wouldn't accept any combinations of usernames or passwords which worked before.
I've reinstalled Ubuntu since then, but I'm just curious about what I did wrong and what I could have done to fix things, for future reference. Thank you~
sudoand of course sudo passwd? :) – Alvar Jan 28 '12 at 15:10