I have this problem on my system as well. I use the radeonhd driver. It goes away if I set /apps/gnome-settings-daemon/plugins/xrandr/active and /apps/gnome_settings_daemon/plugins/xrandr/active both to false (perhaps one of the might have been enough).
Based on Bryce's instructions on IRC, I verified that the driver seems to have xrandr 1.2 support:
xrandr -q reports sensible stuff
xrandr --output VGA_1 --mode 1024x768 sets the mode correctly
xrandr --output VGA_1 --auto correctly resets the mode back to what it should be
I have this problem on my system as well. I use the radeonhd driver. It goes away if I set /apps/gnome- settings- daemon/ plugins/ xrandr/ active and /apps/gnome_ settings_ daemon/ plugins/ xrandr/ active both to false (perhaps one of the might have been enough).
Based on Bryce's instructions on IRC, I verified that the driver seems to have xrandr 1.2 support:
xrandr -q reports sensible stuff
xrandr --output VGA_1 --mode 1024x768 sets the mode correctly
xrandr --output VGA_1 --auto correctly resets the mode back to what it should be