In Ubuntu 13.04 / 12.10 / 12.04, while updating your system you might face this GPG problems.
“W: GPG error: http://archive.ubuntu.com raring Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <firstname.lastname@example.org>
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/download.virtualbox.org_virtualbox_debian_dists_raring_contrib
E: The package lists or status file could not be parsed or opened.”
To Solve this Error
Run the following commands one by one in the terminal (Ctrl+alt+t) and issue the password for the user, when prompted.
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt-get update
To solve duplicate entry error
Error : “W: Duplicate sources.list entry http://archive.canonical.com/ubuntu/ raring/partner i386 Packages (/var/lib/apt/lists/archive.canonical.com_ubuntu_dists_raring_partner_binary-i386_Packages)”
Follow the below link
Hope this will be helpful for you!!!