EDIT: I've created a bug report: https://bugs.freedesktop.org/show_bug.cgi?id=48458

My Setup

I have 4 monitors, 1920x1080, which are in portrait mode (rotated left). They are connected to two radeon graphic cards.

As usual, a picture says more than a thousand words.

The problem

Everything works fine, when Xinerama is disabled. But when I enable Xinerama, things get weird. When I move the mouse of the screen and return, the screen contents begin to move with the mouse, only on this monitor. It seems like the virtual display size does not match the real screen size, which activates a panning viewport. Any idea how to stop this?

The video

I created a video to demonstrate the issue: http://www.youtube.com/watch?v=zq_XHji1P24

xorg.conf

This is my xorg.conf:

Section "ServerLayout"
 ##################[ Evilness begins here ]#############
 Option "Xinerama" "on"       # <--- Makes it go b0rked!
 ##################[    End of all evil   ]#############

 Identifier     "BOFH Console of Doom"
 Screen         0 "Screen-0" 0 0
 Screen         1 "Screen-1" RightOf "Screen-0"
 Screen         2 "Screen-2" RightOf "Screen-1"
 Screen         3 "Screen-3" RightOf "Screen-2"
EndSection

Section "ServerFlags"
  Option "RandR" "false"
EndSection


Section "Module"
  Load  "dbe"
  Load  "dri"
  Load  "extmod"
  Load  "dri2"
  Load  "record"
  Load  "glx"
EndSection

Section "Monitor"
 Identifier   "Monitor-0"
 Option      "Rotate" "left"
EndSection

Section "Monitor"
 Identifier   "Monitor-1"
 Option      "Rotate" "left"
EndSection

Section "Monitor"
 Identifier   "Monitor-2"
 Option      "Rotate" "left"
EndSection

Section "Monitor"
 Identifier   "Monitor-3"
 Option      "Rotate" "left"
EndSection

Section "Device"
 Identifier  "Radeon-0-0"
 Driver      "radeon"
 BusID       "PCI:9:0:0"
 Option      "ZaphodHeads" "DVI-0"
 Screen      0
EndSection

Section "Device"
 Identifier  "Radeon-0-1"
 Driver      "radeon"
 BusID       "PCI:9:0:0"
 Option      "ZaphodHeads" "DVI-1"
 Screen      1
EndSection

Section "Device"
 Identifier  "Radeon-1-0"
 Driver      "radeon"
 BusID       "PCI:4:0:0"
 Option      "ZaphodHeads" "DVI-2"
 Screen      0
EndSection

Section "Device"
 Identifier  "Radeon-1-1"
 Driver      "radeon"
 BusID       "PCI:4:0:0"
 Option      "ZaphodHeads" "DVI-3"
 Screen      1
EndSection

Section "Screen"
 Identifier "Screen-0"
 Device     "Radeon-0-0"
 Monitor    "Monitor-0"
 DefaultDepth     24
 SubSection "Display"
  Viewport   0 0
  Depth     24
 EndSubSection
EndSection

Section "Screen"
 Identifier "Screen-1"
 Device     "Radeon-0-1"
 Monitor    "Monitor-1"
 DefaultDepth     24
 SubSection "Display"
  Viewport   0 0
  Depth     24
 EndSubSection
EndSection

Section "Screen"
 Identifier "Screen-2"
 Device     "Radeon-1-0"
 Monitor    "Monitor-2"
 DefaultDepth     24
 SubSection "Display"
  Viewport   0 0
  Depth     24
 EndSubSection
EndSection

Section "Screen"
 Identifier "Screen-3"
 Device     "Radeon-1-1"
 Monitor    "Monitor-3"
 DefaultDepth     24
 SubSection "Display"
  Viewport   0 0
  Depth     24
 EndSubSection
EndSection