I could do 2 steps as advised in terminal and the output was:

deimos@samsun:~$ sudo dpkg --clear-avail
[sudo] password for deimos: 
deimos@samsun:~$ sudo apt-get update
Hit http://in.archive.ubuntu.com karmic Release.gpg
Ign http://in.archive.ubuntu.com karmic/main Translation-en_IN             
Ign http://in.archive.ubuntu.com karmic/restricted Translation-en_IN        
Ign http://in.archive.ubuntu.com karmic/universe Translation-en_IN          
Ign http://in.archive.ubuntu.com karmic/multiverse Translation-en_IN        
Hit http://in.archive.ubuntu.com karmic-updates Release.gpg                 
Ign http://in.archive.ubuntu.com karmic-updates/main Translation-en_IN
Ign http://in.archive.ubuntu.com karmic-updates/restricted Translation-en_IN
Ign http://in.archive.ubuntu.com karmic-updates/universe Translation-en_IN
Ign http://in.archive.ubuntu.com karmic-updates/multiverse Translation-en_IN
Hit http://in.archive.ubuntu.com karmic Release
Hit http://in.archive.ubuntu.com karmic-updates Release             
Hit http://security.ubuntu.com karmic-security Release.gpg          
Ign http://security.ubuntu.com karmic-security/main Translation-en_IN
Hit http://in.archive.ubuntu.com karmic/main Packages
Hit http://in.archive.ubuntu.com karmic/restricted Packages
Hit http://in.archive.ubuntu.com karmic/main Sources
Hit http://in.archive.ubuntu.com karmic/restricted Sources
Hit http://in.archive.ubuntu.com karmic/universe Packages
Hit http://in.archive.ubuntu.com karmic/universe Sources
Ign http://security.ubuntu.com karmic-security/restricted Translation-en_IN
Ign http://security.ubuntu.com karmic-security/universe Translation-en_IN
Ign http://security.ubuntu.com karmic-security/multiverse Translation-en_IN
Hit http://security.ubuntu.com karmic-security Release
Hit http://in.archive.ubuntu.com karmic/multiverse Packages
Hit http://in.archive.ubuntu.com karmic/multiverse Sources
Hit http://in.archive.ubuntu.com karmic-updates/main Packages
Hit http://in.archive.ubuntu.com karmic-updates/restricted Packages
Hit http://in.archive.ubuntu.com karmic-updates/main Sources
Hit http://in.archive.ubuntu.com karmic-updates/restricted Sources
Hit http://in.archive.ubuntu.com karmic-updates/universe Packages
Hit http://in.archive.ubuntu.com karmic-updates/universe Sources
Hit http://in.archive.ubuntu.com karmic-updates/multiverse Packages
Hit http://in.archive.ubuntu.com karmic-updates/multiverse Sources
Hit http://security.ubuntu.com karmic-security/main Packages
Hit http://security.ubuntu.com karmic-security/restricted Packages
Hit http://security.ubuntu.com karmic-security/main Sources
Hit http://security.ubuntu.com karmic-security/restricted Sources
Hit http://security.ubuntu.com karmic-security/universe Packages
Hit http://security.ubuntu.com karmic-security/universe Sources
Hit http://security.ubuntu.com karmic-security/multiverse Packages
Hit http://security.ubuntu.com karmic-security/multiverse Sources
Reading package lists... Error!
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/in.archive.ubuntu.com_ubuntu_dists_karmic_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.
deimos@samsun:~$ 

I wonder if this is helpful. Regards.

--- On Fri, 26/3/10, Gabe Gorelick <email address hidden> wrote:

From: Gabe Gorelick <email address hidden>
Subject: [Bug 546767] Re: synaptic fails
To: <email address hidden>
Date: Friday, 26 March, 2010, 10:12 PM

I don't see anything obviously wrong with your sources.list. Can you try
to run sudo dpkg --clear-avail in a terminal, and then run sudo apt-get
update, and then try installing packages? See
https://help.ubuntu.com/community/UsingTheTerminal if you need help with
the terminal.

** Changed in: apt (Ubuntu)
       Status: New => Incomplete

-- 
synaptic fails
https://bugs.launchpad.net/bugs/546767
You received this bug notification because you are a direct subscriber
of the bug.

Status in “apt” package in Ubuntu: Incomplete

Bug description:
Binary package hint: ubuntu-docs

Ubuntu9.10 with updates
---------------------------------
When I tried to install a debian package with GDebi the foll message was displayed

Software index is broken

This is a major failure of your software management system. Please check for broken packages with synaptic, check the file permissions and correctness of the file '/etc/apt/sources.list' and reload the software information with: 'sudo apt-get update' and 'sudo apt-get install -f'.
--------------------------
When I open synaptic

E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/in.archive.ubuntu.com_ubuntu_dists_karmic_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.

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