[ubuntu] lost password and now trying to recover...

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http://ubuntuforums.org – i tried to recover my password following the instructions from here (entering also the command: "mount -rw -o remount /") and eveything went smoothly until i rebooted. when i boot up now and the login screen appears i enter my (new) password as usual and then the screen blanks for a moment and "redirects" me back to the login screen. any ideas? im using this laptop both for my work and personal matters so i would be really thankful i someone help me figure this out. (Hardware)