Ubuntu may give you following error message at many places (e.g. with apt-get)
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.
Your need to reset the Merge List. Kindly try following commands ( To remove Merge List, and to to generate new Merge List )
sudo rm /var/lib/apt/lists/* -vf
sudo apt-get update
Bug Report @ https://bugs.launchpad.net/ubuntu/+source/apt/+bug/346386