That happened after I managed to install Virtual Box.
I found a part of the answer here : http://ubuntuforums.org/showthread.php?t=1376802. I added my user to another group and then lost my user to sudoers group. The joke is I haven't any root or admin account - my current user was the sole user of my Ubuntu desktop.
usermod -G cdrom gert
would remove me from all supplementary groups (includingadm
,sudo
, etc.) and only add me tocdrom
(besides the primary group). – gertvdijk Jul 16 '13 at 23:59