DpkgTerminalLog.txt suggests that you have xserver-xorg-video-tseng installed, but the upgrade didn't pull the newer version. There's only one answer to why that happened, and it's that your apt mirror is out of date.
** Changed in: xorg-server (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg-server in ubuntu. https://bugs.launchpad.net/bugs/734676 Title: package xserver-xorg-core 2:1.9.99.902-2ubuntu2 failed to install/upgrade: installing xserver-xorg-core would break existing software _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp