The simple fact to switch to a TTY reactivate the screen. There are also no issues in other windows managers than Gnome (e.g. Openbox), xrandr works well. So probably neither an Xorg nor a driver issue. It seems to be Gnome-related.
** Tags removed: kernel-bug-exists-upstream -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1300914 Title: External screen undetected after first plug Status in “linux” package in Ubuntu: Confirmed Bug description: On Ubuntu 14.04, the external screen plugged on VGA is detected and get activated correctly. However, if I unplug it and then replug it later, it is not detected anymore and the screen receives no signal. A way to get it back to work is to reboot or simply suspend the computer. Sorry but I have no idea of what package is handling that. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1300914/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp