I've only seen outputs named 'default' on -nvidia (which does not support XRANDR). Perhaps you were looking at some out of date directions, or directions for -nvidia instead of -fglrx.
In any case, Brendan is right. According to your xrandr output you don't have a display named 'default' so the error message is correct in this case. ** Changed in: fglrx-installer (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to fglrx-installer in Ubuntu. https://bugs.launchpad.net/bugs/811624 Title: impossible to change resolution with xrandr To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/fglrx-installer/+bug/811624/+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