Triple-Head funktioniert in GDM, aber nicht in Gnome

Ich habe drei Displays, die über DVI auf zwei verschiedenen ATI-Karten unter Arch Linux mit dem xf86-video-atiTreiber verbunden sind.

Alle drei dienen derzeit als Ausgabe, aber eines meiner Displays (das auf der zweiten Karte) fällt nach dem Einloggen in GDM auf einen grauen Bildschirm und einen schwarzen "x" - Cursor.

Erwähnenswert ist, dass die Anzeige auf dem GDM-Anmeldebildschirm funktioniert und den Hintergrund des Anmeldebildschirms rendert (nicht jedoch die Anmeldebox, wie dies bei den beiden anderen Anzeigen der Fall ist).

Wie bekomme ich einen funktionierenden Desktop mit allen drei Displays?

Ich verwende GDM und Gnome3 mit der folgenden xorg.conf:

Section "ServerLayout" Identifier "X.org Configured" Screen 0 "Screen0" 0 0 Screen 1 "Screen1" RightOf "Screen0" Screen 2 "Screen2" RightOf "Screen1" Screen 3 "Screen3" RightOf "Screen2" InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection  Section "Files" ModulePath "/usr/lib/xorg/modules" FontPath "/usr/share/fonts/misc/" FontPath "/usr/share/fonts/TTF/" FontPath "/usr/share/fonts/OTF/" FontPath "/usr/share/fonts/Type1/" FontPath "/usr/share/fonts/100dpi/" FontPath "/usr/share/fonts/75dpi/" EndSection  Section "Module" Load "glx" EndSection  Section "InputDevice" Identifier "Keyboard0" Driver "kbd" EndSection  Section "InputDevice" Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/input/mice" Option "ZAxisMapping" "4 5 6 7" EndSection  Section "Monitor" Identifier "Monitor0" VendorName "Monitor Vendor" ModelName "Monitor Model" EndSection  Section "Monitor" Identifier "Monitor1" VendorName "Monitor Vendor" ModelName "Monitor Model" EndSection  Section "Monitor" Identifier "Monitor2" VendorName "Monitor Vendor" ModelName "Monitor Model" EndSection  Section "Monitor" Identifier "Monitor3" VendorName "Monitor Vendor" ModelName "Monitor Model" EndSection  Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "NoAccel" # [<bool>] #Option "SWcursor" # [<bool>] #Option "EnablePageFlip" # [<bool>] #Option "ColorTiling" # [<bool>] #Option "ColorTiling2D" # [<bool>] #Option "RenderAccel" # [<bool>] #Option "SubPixelOrder" # [<str>] #Option "AccelMethod" # <str> #Option "EXAVSync" # [<bool>] #Option "EXAPixmaps" # [<bool>] #Option "ZaphodHeads" # <str> #Option "EnablePageFlip" # [<bool>] #Option "SwapbuffersWait" # [<bool>] Identifier "Card0" Driver "radeon" BusID "PCI:3:0:0" EndSection  Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "NoAccel" # [<bool>] #Option "SWcursor" # [<bool>] #Option "EnablePageFlip" # [<bool>] #Option "ColorTiling" # [<bool>] #Option "ColorTiling2D" # [<bool>] #Option "RenderAccel" # [<bool>] #Option "SubPixelOrder" # [<str>] #Option "AccelMethod" # <str> #Option "EXAVSync" # [<bool>] #Option "EXAPixmaps" # [<bool>] #Option "ZaphodHeads" # <str> #Option "EnablePageFlip" # [<bool>] #Option "SwapbuffersWait" # [<bool>] Identifier "Card1" Driver "radeon" BusID "PCI:4:0:0" EndSection  Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "ShadowFB" # [<bool>] #Option "DefaultRefresh" # [<bool>] #Option "ModeSetClearScreen" # [<bool>] Identifier "Card2" Driver "vesa" BusID "PCI:3:0:0" EndSection  Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "ShadowFB" # [<bool>] #Option "DefaultRefresh" # [<bool>] #Option "ModeSetClearScreen" # [<bool>] Identifier "Card3" Driver "vesa" BusID "PCI:4:0:0" EndSection  Section "Screen" Identifier "Screen0" Device "Card0" Monitor "Monitor0" SubSection "Display" Viewport 0 0 Depth 1 EndSubSection SubSection "Display" Viewport 0 0 Depth 4 EndSubSection SubSection "Display" Viewport 0 0 Depth 8 EndSubSection SubSection "Display" Viewport 0 0 Depth 15 EndSubSection SubSection "Display" Viewport 0 0 Depth 16 EndSubSection SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection  Section "Screen" Identifier "Screen1" Device "Card1" Monitor "Monitor1" SubSection "Display" Viewport 0 0 Depth 1 EndSubSection SubSection "Display" Viewport 0 0 Depth 4 EndSubSection SubSection "Display" Viewport 0 0 Depth 8 EndSubSection SubSection "Display" Viewport 0 0 Depth 15 EndSubSection SubSection "Display" Viewport 0 0 Depth 16 EndSubSection SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection  Section "Screen" Identifier "Screen2" Device "Card2" Monitor "Monitor2" SubSection "Display" Viewport 0 0 Depth 1 EndSubSection SubSection "Display" Viewport 0 0 Depth 4 EndSubSection SubSection "Display" Viewport 0 0 Depth 8 EndSubSection SubSection "Display" Viewport 0 0 Depth 15 EndSubSection SubSection "Display" Viewport 0 0 Depth 16 EndSubSection SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection  Section "Screen" Identifier "Screen3" Device "Card3" Monitor "Monitor3" SubSection "Display" Viewport 0 0 Depth 1 EndSubSection SubSection "Display" Viewport 0 0 Depth 4 EndSubSection SubSection "Display" Viewport 0 0 Depth 8 EndSubSection SubSection "Display" Viewport 0 0 Depth 15 EndSubSection SubSection "Display" Viewport 0 0 Depth 16 EndSubSection SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection