CAN'T APPLY ADMINSTRATIVE CHANGES

hi i installed KDE 4.0 yesterday on my Hardy.Everything was fine.Then when i wante dto install Superkamba i went to the synaptic and marked superkamba for installation then all the files were downloaded and finally when they had to be applied that is :applying the changes" came the computer took infinite time.Then i restarted a dialog cam which told me that i can't apply any changes all i can do is download them.
So i tried installing some other program which again showed the same result as Superkamba.
ok here are somethings u wud like to see
 when i did
 [code]sudo adduser pardesi admin[/code]
the result was
[code]The user 'pardesi' is already a member of 'admin'[/code]

when i did
[code]sudo cat /etc/sudoers[/code]
i get
[code]# /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
# Host alias specification

# User alias specification

# Cmnd alias specification

# Defaults

Defaults !lecture,tty_tickets,!fqdn

# User privilege specification
root ALL=(ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL[/code]

when i did
[code]sudo -l[/code]
i get
[code]User pardesi may run the following commands on this host:
    (ALL) ALL[/code]

thanks