install the package http://launchpadlibrarian.net/262502497/xserver- xorg-core-lts-vivid_1.17.1-0ubuntu3.1~trusty1.1_amd64.deb and tested again, this issue has gone.
** Tags removed: verification-needed ** Tags added: verification-done -- 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/1586260 Title: System freeze & no display if set External monitor as primary (Performance mode) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1586260/+subscriptions _______________________________________________ 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
