Changing refresh rate is done via nvidia-settings dialog instead of the gnome displays settings one for these drivers, sorry you got caught up in an automated bug bot fight :) The livecd uses nouveau and the gnome settings applet works there, you checked enable third party drivers during the install so it automatically installed nvidia again after.
** Package changed: xorg-server (Ubuntu) => nvidia-graphics-drivers (Ubuntu) -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to nvidia-graphics-drivers in Ubuntu. https://bugs.launchpad.net/bugs/958439 Title: Doesn't detect monitor / "Unknown", causes flickering / low refresh rate To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/958439/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : [email protected] Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp

