These are the errors shows by different client Update Manager:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 968, in simulate
    trans.unauthenticated = self._simulate_helper(trans)
  File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1092, in _simulate_helper
    return depends, self._cache.required_download, \
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 235, in required_download
    pm.get_archives(fetcher, self._list, self._records)
SystemError: E:Method  has died unexpectedly!, 
    E:Sub-process  returned an error code (100), 
    E:Method /usr/lib/apt/methods/ did not start correctly

Synaptic package Manager

E: Method  has died unexpectedly!
E: Sub-process  returned an error code (100)
E: Method /usr/lib/apt/methods/ did not start correctly
E: Unable to lock the download directory

Command: sudo apt-get upgrade

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be upgraded:
  libfreetype6 libfreetype6-dev
2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Failed to exec method /usr/lib/apt/methods/
E: Method  has died unexpectedly!
E: Sub-process  returned an error code (100)
E: Method /usr/lib/apt/methods/ did not start correctly

Can anyone one tell me how to resolve these issues ?
I have no volatile packages or anything so i am even posting the preview of my sources.list file.

# deb cdrom:[Ubuntu 10.10 _Maverick Meerkat_ - Release i386 (20101007)]/ maverick main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://in.archive.ubuntu.com/ubuntu/ oneiric main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ oneiric universe
deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://in.archive.ubuntu.com/ubuntu/ oneiric multiverse
deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://in.archive.ubuntu.com/ubuntu/ maverick-backports main restricted universe multiverse
# deb-src http://in.archive.ubuntu.com/ubuntu/ maverick-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu oneiric partner
deb-src http://archive.canonical.com/ubuntu oneiric partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu oneiric main
deb-src http://extras.ubuntu.com/ubuntu oneiric main

deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security main restricted
deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security universe
deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security multiverse

# deb http://archive.canonical.com/ lucid partner

Here is the preview of my sources.list file