我最近将我的华硕 N550JV 笔记本电脑从 raving 升级到了 saucy，一开始，只需安装nvidia-319并nvidia-prime运行就非常顺畅（如描述的那样这里）。
升级完成后不久，我更新了所有软件源并执行了dist-upgrade，但不知何故却破坏了nvidia-prime。我尝试重新安装它并安装了一个较新版本什么都没起作用。
这是我的相关摘录/var/log/Xorg.0.log：
[ 7.636] (II) Module glx: vendor="NVIDIA Corporation"
[ 7.636] (II) NVIDIA GLX Module 331.38 Wed Jan 8 19:10:17 PST 2014
[ 7.641] (II) Module nvidia: vendor="NVIDIA Corporation"
[ 7.643] (II) NVIDIA dlloader X Driver 331.38 Wed Jan 8 18:51:00 PST 2014
[ 7.643] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[ 7.647] (II) NVIDIA(0): Creating default Display subsection in Screen section
[ 7.647] (==) NVIDIA(0): Depth 24, (==) framebuffer bpp 32
[ 7.647] (==) NVIDIA(0): RGB weight 888
[ 7.647] (==) NVIDIA(0): Default visual is TrueColor
[ 7.647] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
[ 7.647] (**) NVIDIA(0): Option "UseDisplayDevice" "none"
[ 7.647] (**) NVIDIA(0): Enabling 2D acceleration
[ 7.647] (**) NVIDIA(0): Option "UseDisplayDevice" set to "none"; enabling NoScanout
[ 7.647] (**) NVIDIA(0): mode
[ 8.727] (II) NVIDIA(GPU-0): Found DRM driver nvidia-drm (20130102)
[ 8.728] (II) NVIDIA(0): NVIDIA GPU GeForce GT 750M (GK107) at PCI:1:0:0 (GPU-0)
[ 8.728] (--) NVIDIA(0): Memory: 4194304 kBytes
[ 8.728] (--) NVIDIA(0): VideoBIOS: 80.07.9a.00.4b
[ 8.728] (II) NVIDIA(0): Detected PCI Express Link width: 16X
[ 8.728] (--) NVIDIA(0): Valid display device(s) on GeForce GT 750M at PCI:1:0:0
[ 8.728] (--) NVIDIA(0): none
[ 8.728] (II) NVIDIA(0): Validated MetaModes:
[ 8.728] (II) NVIDIA(0): "NULL"
[ 8.728] (II) NVIDIA(0): Virtual screen size determined to be 640 x 480
[ 8.728] (WW) NVIDIA(0): Unable to get display device for DPI computation.
[ 8.728] (==) NVIDIA(0): DPI set to (75, 75); computed from built-in default
[ 9.824] (II) NVIDIA: Using 3072.00 MB of virtual memory for indirect memory
[ 9.824] (II) NVIDIA: access.
[ 9.829] (II) NVIDIA(0): Setting mode "NULL"
[ 9.829] (EE) NVIDIA(0): Failed to initiate mode change.
[ 9.829] (EE) NVIDIA(0): Failed to complete mode change
[ 9.838] (II) NVIDIA(0): Built-in logo is bigger than the screen.
[ 9.842] (==) NVIDIA(0): Disabling shared memory pixmaps
[ 9.842] (==) NVIDIA(0): Backing store disabled
[ 9.842] (==) NVIDIA(0): Silken mouse enabled
[ 9.842] (==) NVIDIA(0): DPMS enabled
[ 9.842] (II) NVIDIA(0): [DRI2] Setup complete
[ 9.842] (II) NVIDIA(0): [DRI2] VDPAU driver: nvidia
这是在我的计算机上生成的/etc/X11/xorg.conf文件：nvidia-prime
# Warning: This file is autogenerated by nvidia-prime. All changes to this file will be lost.
Section "ServerLayout"
Identifier "layout"
Screen 0 "nvidia"
Inactive "intel"
EndSection
Section "Device"
Identifier "nvidia"
Driver "nvidia"
BusID "1:0:0"
EndSection
Section "Screen"
Identifier "nvidia"
Device "nvidia"
# The internal display might not be connected
# to the nvidia card but we definitely want
# to be able to connect external displays later
#Option "AllowEmptyInitialConfiguration" "on"
Option "UseDisplayDevice" "none"
EndSection
Section "Device"
Identifier "intel"
Driver "modesetting"
EndSection
Section "Screen"
Identifier "intel"
Device "intel"
EndSection
我该如何解决这个错误？