I just found out that this happens only after I log out of gnome and back in again, or if I reset the X server using control+alt+backspace. After a full restart, the system behaves normally. gnome settings still show the non-existent screen, but the mouse pointer cannot wander into its "territory", and apps behave normally.
** Summary changed: - X recognises a non-existent screen + After logging out and back in, X recognises a non-existent screen -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2061239 Title: After logging out and back in, X recognises a non-existent screen To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/x11-xserver-utils/+bug/2061239/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
