I've installed nvidia-current using the Additional Drivers application in Ubuntu 12.04. I need those drivers so I can use accelerated WebGL.

After installing the drivers, and rebooting X fails to start and I have a frozen system/dark screen.

Below is the content of Xorg.0.log

How can I fix this problem?

    [     4.666] 
X.Org X Server 1.11.3
Release Date: 2011-12-16
[     4.666] X Protocol Version 11, Revision 0
[     4.666] Build Operating System: Linux 2.6.42-23-generic x86_64 Ubuntu
[     4.666] Current Operating System: Linux david-macbook-air 3.2.0-34-generic #53-Ubuntu SMP Thu Nov 15 10:48:16 UTC 2012 x86_64
[     4.666] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.2.0-34-generic root=UUID=b3d5ae2a-72af-4ef9-b775-0d40b5f80f9b ro quiet splash vt.handoff=7
[     4.666] Build Date: 29 August 2012  12:12:33AM
[     4.666] xorg-server 2:1.11.4-0ubuntu10.8 (For technical support please see http://www.ubuntu.com/support) 
[     4.666] Current version of pixman: 0.24.4
[     4.666]    Before reporting problems, check http://wiki.x.org
    to make sure that you have the latest version.
[     4.666] Markers: (--) probed, (**) from config file, (==) default setting,
    (++) from command line, (!!) notice, (II) informational,
    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[     4.666] (==) Log file: "/var/log/Xorg.0.log", Time: Thu Dec 13 10:18:02 2012
[     4.668] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[     4.668] (==) No Layout section.  Using the first Screen section.
[     4.668] (==) No screen section available. Using defaults.
[     4.668] (**) |-->Screen "Default Screen Section" (0)
[     4.668] (**) |   |-->Monitor "<default monitor>"
[     4.668] (==) No monitor specified for screen "Default Screen Section".
    Using a default monitor configuration.
[     4.668] (==) Automatically adding devices
[     4.668] (==) Automatically enabling devices
[     4.668] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[     4.668]    Entry deleted from font path.
[     4.668] (WW) The directory "/usr/share/fonts/X11/100dpi/" does not exist.
[     4.668]    Entry deleted from font path.
[     4.669] (WW) The directory "/usr/share/fonts/X11/75dpi/" does not exist.
[     4.669]    Entry deleted from font path.
[     4.669] (WW) The directory "/usr/share/fonts/X11/100dpi" does not exist.
[     4.669]    Entry deleted from font path.
[     4.669] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist.
[     4.669]    Entry deleted from font path.
[     4.669] (WW) The directory "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType" does not exist.
[     4.669]    Entry deleted from font path.
[     4.669] (==) FontPath set to:
    /usr/share/fonts/X11/misc,
    /usr/share/fonts/X11/Type1,
    built-ins
[     4.669] (==) ModulePath set to "/usr/lib/x86_64-linux-gnu/xorg/extra-modules,/usr/lib/xorg/extra-modules,/usr/lib/xorg/modules"
[     4.669] (II) The server relies on udev to provide the list of input devices.
    If no devices become available, reconfigure udev or disable AutoAddDevices.
[     4.669] (II) Loader magic: 0x7f6222467b00
[     4.669] (II) Module ABI versions:
[     4.669]    X.Org ANSI C Emulation: 0.4
[     4.669]    X.Org Video Driver: 11.0
[     4.669]    X.Org XInput driver : 16.0
[     4.669]    X.Org Server Extension : 6.0
[     4.670] (--) PCI:*(0:2:0:0) 10de:08a3:106b:00d3 rev 162, Mem @ 0x92000000/16777216, 0x80000000/268435456, 0x90000000/33554432, I/O @ 0x00001000/128, BIOS @ 0x????????/131072
[     4.670] (II) Open ACPI successful (/var/run/acpid.socket)
[     4.670] (II) LoadModule: "extmod"
[     4.671] (II) Loading /usr/lib/xorg/modules/extensions/libextmod.so
[     4.671] (II) Module extmod: vendor="X.Org Foundation"
[     4.671]    compiled for 1.11.3, module version = 1.0.0
[     4.671]    Module class: X.Org Server Extension
[     4.671]    ABI class: X.Org Server Extension, version 6.0
[     4.671] (II) Loading extension MIT-SCREEN-SAVER
[     4.671] (II) Loading extension XFree86-VidModeExtension
[     4.671] (II) Loading extension XFree86-DGA
[     4.671] (II) Loading extension DPMS
[     4.671] (II) Loading extension XVideo
[     4.671] (II) Loading extension XVideo-MotionCompensation
[     4.671] (II) Loading extension X-Resource
[     4.671] (II) LoadModule: "dbe"
[     4.671] (II) Loading /usr/lib/xorg/modules/extensions/libdbe.so
[     4.671] (II) Module dbe: vendor="X.Org Foundation"
[     4.671]    compiled for 1.11.3, module version = 1.0.0
[     4.671]    Module class: X.Org Server Extension
[     4.671]    ABI class: X.Org Server Extension, version 6.0
[     4.671] (II) Loading extension DOUBLE-BUFFER
[     4.671] (II) LoadModule: "glx"
[     4.671] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/libglx.so
[     4.869] (II) Module glx: vendor="NVIDIA Corporation"
[     4.869]    compiled for 4.0.2, module version = 1.0.0
[     4.869]    Module class: X.Org Server Extension
[     4.869] (II) NVIDIA GLX Module  295.40  Thu Apr  5 21:57:38 PDT 2012
[     4.869] (II) Loading extension GLX
[     4.869] (II) LoadModule: "record"
[     4.870] (II) Loading /usr/lib/xorg/modules/extensions/librecord.so
[     4.870] (II) Module record: vendor="X.Org Foundation"
[     4.870]    compiled for 1.11.3, module version = 1.13.0
[     4.870]    Module class: X.Org Server Extension
[     4.870]    ABI class: X.Org Server Extension, version 6.0
[     4.870] (II) Loading extension RECORD
[     4.870] (II) LoadModule: "dri"
[     4.870] (II) Loading /usr/lib/xorg/modules/extensions/libdri.so
[     4.870] (II) Module dri: vendor="X.Org Foundation"
[     4.870]    compiled for 1.11.3, module version = 1.0.0
[     4.870]    ABI class: X.Org Server Extension, version 6.0
[     4.870] (II) Loading extension XFree86-DRI
[     4.870] (II) LoadModule: "dri2"
[     4.871] (II) Loading /usr/lib/xorg/modules/extensions/libdri2.so
[     4.871] (II) Module dri2: vendor="X.Org Foundation"
[     4.871]    compiled for 1.11.3, module version = 1.2.0
[     4.871]    ABI class: X.Org Server Extension, version 6.0
[     4.871] (II) Loading extension DRI2
[     4.871] (==) Matched nvidia as autoconfigured driver 0
[     4.871] (==) Matched nouveau as autoconfigured driver 1
[     4.871] (==) Matched nv as autoconfigured driver 2
[     4.871] (==) Matched vesa as autoconfigured driver 3
[     4.871] (==) Matched fbdev as autoconfigured driver 4
[     4.871] (==) Assigned the driver to the xf86ConfigLayout
[     4.871] (II) LoadModule: "nvidia"
[     4.871] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so
[     4.887] (II) Module nvidia: vendor="NVIDIA Corporation"
[     4.887]    compiled for 4.0.2, module version = 1.0.0
[     4.887]    Module class: X.Org Video Driver
[     4.892] (II) LoadModule: "nouveau"
[     4.894] (II) Loading /usr/lib/xorg/modules/drivers/nouveau_drv.so
[     4.894] (II) Module nouveau: vendor="X.Org Foundation"
[     4.894]    compiled for 1.11.3, module version = 1.0.2
[     4.894]    Module class: X.Org Video Driver
[     4.894]    ABI class: X.Org Video Driver, version 11.0
[     4.894] (II) LoadModule: "nv"
[     4.895] (WW) Warning, couldn't open module nv
[     4.895] (II) UnloadModule: "nv"
[     4.895] (II) Unloading nv
[     4.895] (EE) Failed to load module "nv" (module does not exist, 0)
[     4.895] (II) LoadModule: "vesa"
[     4.895] (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so
[     4.896] (II) Module vesa: vendor="X.Org Foundation"
[     4.896]    compiled for 1.11.3, module version = 2.3.0
[     4.896]    Module class: X.Org Video Driver
[     4.896]    ABI class: X.Org Video Driver, version 11.0
[     4.896] (II) LoadModule: "fbdev"
[     4.896] (II) Loading /usr/lib/xorg/modules/drivers/fbdev_drv.so
[     4.896] (II) Module fbdev: vendor="X.Org Foundation"
[     4.896]    compiled for 1.11.3, module version = 0.4.2
[     4.896]    ABI class: X.Org Video Driver, version 11.0
[     4.896] (==) Matched nvidia as autoconfigured driver 0
[     4.896] (==) Matched nouveau as autoconfigured driver 1
[     4.896] (==) Matched nv as autoconfigured driver 2
[     4.896] (==) Matched vesa as autoconfigured driver 3
[     4.896] (==) Matched fbdev as autoconfigured driver 4
[     4.896] (==) Assigned the driver to the xf86ConfigLayout
[     4.896] (II) LoadModule: "nvidia"
[     4.896] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so
[     4.896] (II) Module nvidia: vendor="NVIDIA Corporation"
[     4.896]    compiled for 4.0.2, module version = 1.0.0
[     4.896]    Module class: X.Org Video Driver
[     4.896] (II) UnloadModule: "nvidia"
[     4.896] (II) Unloading nvidia
[     4.896] (II) Failed to load module "nvidia" (already loaded, 32610)
[     4.896] (II) LoadModule: "nouveau"
[     4.897] (II) Loading /usr/lib/xorg/modules/drivers/nouveau_drv.so
[     4.897] (II) Module nouveau: vendor="X.Org Foundation"
[     4.897]    compiled for 1.11.3, module version = 1.0.2
[     4.897]    Module class: X.Org Video Driver
[     4.897]    ABI class: X.Org Video Driver, version 11.0
[     4.897] (II) UnloadModule: "nouveau"
[     4.897] (II) Unloading nouveau
[     4.897] (II) Failed to load module "nouveau" (already loaded, 32610)
[     4.897] (II) LoadModule: "nv"
[     4.897] (WW) Warning, couldn't open module nv
[     4.897] (II) UnloadModule: "nv"
[     4.897] (II) Unloading nv
[     4.897] (EE) Failed to load module "nv" (module does not exist, 0)
[     4.897] (II) LoadModule: "vesa"
[     4.898] (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so
[     4.898] (II) Module vesa: vendor="X.Org Foundation"
[     4.898]    compiled for 1.11.3, module version = 2.3.0
[     4.898]    Module class: X.Org Video Driver
[     4.898]    ABI class: X.Org Video Driver, version 11.0
[     4.898] (II) UnloadModule: "vesa"
[     4.898] (II) Unloading vesa
[     4.898] (II) Failed to load module "vesa" (already loaded, 0)
[     4.898] (II) LoadModule: "fbdev"
[     4.898] (II) Loading /usr/lib/xorg/modules/drivers/fbdev_drv.so
[     4.898] (II) Module fbdev: vendor="X.Org Foundation"
[     4.898]    compiled for 1.11.3, module version = 0.4.2
[     4.898]    ABI class: X.Org Video Driver, version 11.0
[     4.898] (II) UnloadModule: "fbdev"
[     4.898] (II) Unloading fbdev
[     4.899] (II) Failed to load module "fbdev" (already loaded, 0)
[     4.899] (II) NVIDIA dlloader X Driver  295.40  Thu Apr  5 21:38:35 PDT 2012
[     4.899] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[     4.899] (II) NOUVEAU driver Date:   Wed Sep 12 13:42:43 2012 +0200
[     4.899] (II) NOUVEAU driver for NVIDIA chipset families :
[     4.899]    RIVA TNT        (NV04)
[     4.899]    RIVA TNT2       (NV05)
[     4.899]    GeForce 256     (NV10)
[     4.899]    GeForce 2       (NV11, NV15)
[     4.899]    GeForce 4MX     (NV17, NV18)
[     4.899]    GeForce 3       (NV20)
[     4.900]    GeForce 4Ti     (NV25, NV28)
[     4.900]    GeForce FX      (NV3x)
[     4.900]    GeForce 6       (NV4x)
[     4.900]    GeForce 7       (G7x)
[     4.900]    GeForce 8       (G8x)
[     4.900]    GeForce GTX 200 (NVA0)
[     4.900]    GeForce GTX 400 (NVC0)
[     4.900] (II) VESA: driver for VESA chipsets: vesa
[     4.900] (II) FBDEV: driver for framebuffer: fbdev
[     4.900] (++) using VT number 7

[     4.902] (II) Loading sub module "fb"
[     4.902] (II) LoadModule: "fb"
[     4.902] (II) Loading /usr/lib/xorg/modules/libfb.so
[     4.902] (II) Module fb: vendor="X.Org Foundation"
[     4.902]    compiled for 1.11.3, module version = 1.0.0
[     4.902]    ABI class: X.Org ANSI C Emulation, version 0.4
[     4.902] (II) Loading sub module "wfb"
[     4.902] (II) LoadModule: "wfb"
[     4.903] (II) Loading /usr/lib/xorg/modules/libwfb.so
[     4.905] (II) Module wfb: vendor="X.Org Foundation"
[     4.905]    compiled for 1.11.3, module version = 1.0.0
[     4.905]    ABI class: X.Org ANSI C Emulation, version 0.4
[     4.905] (II) Loading sub module "ramdac"
[     4.905] (II) LoadModule: "ramdac"
[     4.905] (II) Module "ramdac" already built-in
[     4.907] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so
[     4.907] (II) Loading /usr/lib/xorg/modules/libwfb.so
[     4.907] (II) Loading /usr/lib/xorg/modules/libfb.so
[     4.912] (WW) Falling back to old probe method for vesa
[     4.912] (WW) Falling back to old probe method for fbdev
[     4.912] (II) Loading sub module "fbdevhw"
[     4.912] (II) LoadModule: "fbdevhw"
[     4.912] (II) Loading /usr/lib/xorg/modules/libfbdevhw.so
[     4.912] (II) Module fbdevhw: vendor="X.Org Foundation"
[     4.912]    compiled for 1.11.3, module version = 0.0.2
[     4.912]    ABI class: X.Org Video Driver, version 11.0
[     4.912] (II) NVIDIA(0): Creating default Display subsection in Screen section
    "Default Screen Section" for depth/fbbpp 24/32
[     4.912] (==) NVIDIA(0): Depth 24, (==) framebuffer bpp 32
[     4.912] (==) NVIDIA(0): RGB weight 888
[     4.912] (==) NVIDIA(0): Default visual is TrueColor
[     4.912] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
[     4.912] (**) NVIDIA(0): Enabling 2D acceleration
[     5.442] (EE) NVIDIA(0): Failed to initialize the display subsystem for the NVIDIA
[     5.442] (EE) NVIDIA(0):     graphics device!
[     5.442] (EE) NVIDIA(0): Failed to get supported display device(s)
[     5.442] (EE) NVIDIA(0): Failed to initialize dac HAL
[     5.442] (II) UnloadModule: "nvidia"
[     5.442] (II) Unloading nvidia
[     5.442] (II) UnloadModule: "wfb"
[     5.442] (II) Unloading wfb
[     5.442] (II) UnloadModule: "fb"
[     5.443] (II) Unloading fb
[     5.443] (EE) Screen(s) found, but none have a usable configuration.
[     5.443] 
Fatal server error:
[     5.443] no screens found
[     5.443] 
Please consult the The X.Org Foundation support 
     at http://wiki.x.org
 for help. 
[     5.443] Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[     5.443] 
[     5.447]  ddxSigGiveUp: Closing log
[     5.447] Server terminated with error (1). Closing log file.