MSI N8400GS (NVIDIA) on Ubuntu 12.04

Question

Trying to get MSI N8400GS (NVIDIA) graphics card working on Ubuntu 12.04. It was working fine till the upgrade, now the system hangs at "Checking Battery Status". If I do I can get to a terminal, but startx doesn't work from there either. I've spent the last two days trying to fix this, including installing the latest drivers from NVIDIA, and various fixes such as blacklisting nouveau. However I'm no further on - any help would be greatly appreciated!

Some debugging output below:

$ lspci -nnk | grep -i VGA

01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GT218 [GeForce 8400 GS] [10de:10c3] (rev a2)

$ /usr/lib/nux/unity_support_test --print
OpenGL vendor string:   Mesa Project
OpenGL renderer string: Software Rasterizer
OpenGL version string:  1.4 (2.1 Mesa 7.10.2)
Not software rendered:    no
Not blacklisted:          yes
GLX fbconfig:             yes
GLX texture from pixmap:  yes
GL npot or rect textures: yes
GL vertex program:        yes
GL fragment program:      yes
GL vertex buffer object:  no
GL framebuffer object:    yes
GL version is 1.4+:       yes
Unity 3D supported:       no

$ sudo hwinfo --gfxcard
 23: PCI 100.0: 0300 VGA compatible controller (VGA)            
  [Created at pci.318]
  UDI: /org/freedesktop/Hal/devices/pci_10de_10c3
  Unique ID: VCu0.awsjQ3tXCG4
  Parent ID: vSkL.NPX2MgnEFQ0
  SysFS ID: /devices/pci0000:00/0000:00:01.0/0000:01:00.0
  SysFS BusID: 0000:01:00.0
  Hardware Class: graphics card
  Model: "nVidia VGA compatible controller"
  Vendor: pci 0x10de "nVidia Corporation"
  Device: pci 0x10c3
  SubVendor: pci 0x1462 "Micro-Star International Co., Ltd."
  SubDevice: pci 0x2400
  Revision: 0xa2
  Driver: "nvidia"
  Driver Modules: "nvidia"
  Memory Range: 0xfa000000-0xfaffffff (rw,non-prefetchable)
  Memory Range: 0xc0000000-0xcfffffff (ro,non-prefetchable)
  Memory Range: 0xd0000000-0xd1ffffff (ro,non-prefetchable)
  I/O Ports: 0xe000-0xefff (rw)
  Memory Range: 0xfb000000-0xfb07ffff (ro,non-prefetchable,disabled)
  IRQ: 16 (16841 events)
  I/O Ports: 0x3c0-0x3df (rw)
  Module Alias: "pci:v000010DEd000010C3sv00001462sd00002400bc03sc00i00"
  Driver Info #0:
    Driver Status: nvidiafb is not active
    Driver Activation Cmd: "modprobe nvidiafb"
  Driver Info #1:
    Driver Status: nouveau is not active
    Driver Activation Cmd: "modprobe nouveau"
  Driver Info #2:
    Driver Status: nvidia is active
    Driver Activation Cmd: "modprobe nvidia"
  Driver Info #3:
    Driver Status: nvidia_current is not active
    Driver Activation Cmd: "modprobe nvidia_current"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #10 (PCI bridge)
Primary display adapter: #23

$ echo $DESKTOP_SESSION

(blank)