Error upgrading xlibs to testing

after editing the /etc/apt/sources.list I ran > apt-get update > apt-get dist-upgrade and then got the following error Preparing to replace xlibs 4.1.0-16 (using .../xlibs_4.2.1-3_i386.deb) ... Unpacking replacement xlibs ... dpkg: error processing /var/cache/apt/archives/xlibs_4.2.1-3_i386.deb

Error upgrading xlibs to testing

after editing the /etc/apt/sources.list I ran > apt-get update > apt-get dist-upgrade and then got the following error Preparing to replace xlibs 4.1.0-16 (using .../xlibs_4.2.1-3_i386.deb) ... Unpacking replacement xlibs ... dpkg: error processing /var/cache/apt/archives/xlibs_4.2.1-3_i386.deb