package syslinux-common 3:4.05+dfsg-6+deb7u2ubuntu1 failed to install/upgrade: ErrorMessage: package syslinux-common is already installed and configured

Thanks for taking the time to report this bug and helping to make Ubuntu better. We appreciate the difficulties you are facing, but this appears to be a "regular" (non-security) bug. I have unmarked it as a security issue since this bug does not show evidence of allowing attackers to cross privilege boundaries nor directly cause loss of data/privacy. Please feel free to report any other bugs you may find.

The initial error here is due to a corrupt package but then dpkg tries to configure the package that failed to unpack:

2013-10-18 09:38:19,042 DEBUG failed to SystemUnLock() (E:Not locked)
2013-10-18 10:07:48,209 ERROR got an error from dpkg for pkg: '/var/cache/apt/archives/syslinux-common_3%3a4.05+dfsg-6+deb7u3ubuntu1_all.deb': 'cannot copy extracted data for './usr/share/doc/syslinux/CodingStyle.txt.gz' to '/usr/share/doc/syslinux/CodingStyle.txt.gz.dpkg-new': unexpected end of file or stream'
2013-10-18 10:07:48,209 DEBUG running apport_pkgfailure() syslinux-common: cannot copy extracted data for './usr/share/doc/syslinux/CodingStyle.txt.gz' to '/usr/share/doc/syslinux/CodingStyle.txt.gz.dpkg-new': unexpected end of file or stream
2013-10-18 10:07:48,210 WARNING Failed to determine apport version (No module named apport.ui)
2013-10-18 10:07:48,217 ERROR got an error from dpkg for pkg: '/var/cache/apt/archives/syslinux-common_3%3a4.05+dfsg-6+deb7u3ubuntu1_all.deb': 'cannot copy extracted data for './usr/share/doc/syslinux/CodingStyle.txt.gz' to '/usr/share/doc/syslinux/CodingStyle.txt.gz.dpkg-new': unexpected end of file or stream'
2013-10-18 10:08:52,691 ERROR got an error from dpkg for pkg: 'syslinux-common': 'package syslinux-common is already installed and configured'
2013-10-18 10:08:52,691 DEBUG running apport_pkgfailure() syslinux-common: package syslinux-common is already installed and configured