Comment 12 for bug 183873

This seems to be fixed in the latest version of Ubuntu:

$ dpkg -s xserver-xorg-video-ati | grep Version
Version: 1:6.7.197-1ubuntu1
$ dpkg -s x11-xserver-utils | grep Version
Version: 7.3+2
$ xrandr
Screen 0: minimum 320 x 200, current 2880 x 1200, maximum 2880 x 1200
VGA-0 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 408mm x 306mm
   1600x1200 60.0*+ 59.9
   1280x1024 84.8 75.0 59.9
   1280x960 59.9
   1152x864 75.0
   1024x768 84.9 75.1 60.0
   832x624 74.6
   800x600 84.9 60.3
   640x480 84.6 75.0 60.0
   720x400 70.1
DVI-0 connected 1280x1024+1600+0 (normal left inverted right x axis y axis) 360mm x 290mm
   1280x1024 75.0*+ 59.9
   1152x864 75.0
   1024x768 75.1 70.1 60.0
   832x624 74.6
   800x600 72.2 75.0 60.3 56.2
   640x480 75.0 72.8 66.7 60.0
   720x400 70.1
LVDS connected (normal left inverted right x axis y axis)
   1400x1050 59.9
S-video disconnected (normal left inverted right x axis y axis)