i can not run updates

[abhishek]

i can not run update manager it
flags
Could not initialize the package information

An unresolvable problem occurred while initializing the package information.

Please report this bug against the 'update-manager' package and include the following error message:

'E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/archive.canonical.com_ubuntu_dists_natty_partner_binary-amd64_Packages, E:The package lists or status file could not be parsed or opened.'

and when i try ubuntu tweek it gives

this module encountered an error wile loading
and its error message is

Distribution: Ubuntu 11.04 natty
Application: Ubuntu Tweak 0.5.13
Desktop: gnome

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/mainwindow.py", line 502, in setup_notebook
    page = module()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/updatemanager.py", line 44, in __init__
    self.update_list()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/updatemanager.py", line 59, in update_list
    PACKAGE_WORKER.update_apt_cache(init=True)
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/common/package.py", line 226, in update_apt_cache
    self.cache = apt.Cache()
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 89, in __init__
    self.open(progress)
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 127, in open
    self._cache = apt_pkg.Cache(progress)
SystemError: E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/archive.canonical.com_ubuntu_dists_natty_partner_binary-amd64_Packages, E:The package lists or status file could not be parsed or opened.

guys help me out.
thanks,

[Tushar Jain (tushaar-iitr)]

any solution???