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I've been using Lubuntu 12.04 on a somewhat unusual multi-display configuration; 3 displays arranged horizontally, and a fourth centred above them. This had been working fine in 12.04, but when upgrading to 13.04, xrandr is failing to set the resolution of the middle display:

xrandr  --output DVI-1         --mode 1920x1080 --rate 60 \
        --output HDMI-0        --mode 1680x1050 --rate 60 --right-of DVI-1 \
        --output DVI-0         --mode 1280x1024 --rate 60 --left-of DVI-1 \
        --output DisplayPort-0 --mode 1280x1024 --rate 60 --above DVI-1

While the screens are arranged correctly, the middle display (DVI-1) remains at 1280x1024 resolution (as it had been at startup), even though xrandr says it's at 1920x1080.

If I run xrandr --output DVI-1 --off the display is turned off, but running the above command again won't turn it back on, even though again xrandr claims it's on. The Monitor Settings page in Applications -> Preferences -> Monitor Settings also claims the display is on and running at 1920x1080. xrandr doesn't produce any output when setting the resolution.

Additionally, no windows will appear on the middle display. It's as if they go behind the desktop image. I can drag them across to another display and they'll appear fine there.

Finally, my mouse cursor is now about twice its normal size when it's in the normal "pointer" mode. Other pointers such as the text cursor appear normal.

All four displays are connected to a Radeon HD 5770 using the default open-source driver xserver-xorg-video-ati. I have no xorg.conf.

xrandr shows the supported resolutions correctly and thinks it's in 1920x1080:

Screen 0: minimum 320 x 200, current 4880 x 2104, maximum 8192 x 8192
DisplayPort-0 connected 1280x1024+1280+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024      60.0*+   75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
HDMI-0 connected 1680x1050+3200+1024 (normal left inverted right x axis y axis) 473mm x 296mm
   1680x1050      59.9 +   60.0* 
   1920x1080i     25.0     30.0  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1280x960       60.0  
   1152x864       75.0  
   1280x720       50.0     60.0  
   1024x768       75.1     60.0  
   832x624        74.6  
   800x600        75.0     60.3     56.2  
   720x576        50.0  
   720x480        59.9  
   640x480        75.0     60.0     59.9  
   720x400        70.1  
DVI-0 connected 1280x1024+0+1024 (normal left inverted right x axis y axis) 376mm x 301mm
   1280x1024      60.0*+   75.0  
   1280x960       60.0  
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
DVI-1 connected 1920x1080+1280+1024 (normal left inverted right x axis y axis) 510mm x 287mm
   1920x1080      60.0*+   50.0  
   1600x1200      60.0  
   1680x1050      59.9  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1280x960       60.0  
   1280x800       59.9  
   1152x864       75.0  
   1280x720       50.0     60.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   720x576        50.0  
   720x480        59.9  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  

Photos here show the configuration and rendering issues: http://imgur.com/uDAwA5n&MRpYpv6

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