Ubuntu 12.10 upgrade breaks my VM [closed]

Question

I'm sorry if this has been asked before.

A little background: I have to use an Ubuntu VM for work (host is Windows 7 x64, running Oracle VMWare 4.2.4r81684 on a HP ProBook 4730s laptop), mainly for low level network control. So, I installed Ubuntu 12.04, this was a few weeks back.

I set the upgrade process going a few days ago and let my VM do it's stuff. When I came back several hours later, the upgrade process had crashed - I can't remember the error message exactly, but it was something along the lines of one of the Quantal software servers being unreachable. I was prompted to reboot and did... foolishly.

Once the VM had rebooted, I logged on and was presented with the Quantal wallpaper only. I noticed that my mouse movements weren't being mapped correctly and that some keystrokes weren't being accepted first time. Several minutes later, I was prompted about a problem having occurred and was asked if I'd like to send a bug report.

The application unity greeter has closed unexpectedly.

Executable path: /usr/bin/unity-greeter

I hit Ctrl+Alt and T and issued the following commands

dconf reset -f /org/compiz/
setsid unity

In the log that was spat out, I noticed something along the lines of

OpenGL Illegal instruction*

I needed to boot into this VM (I figured it'd be quicker to fix this, than re-install Ubuntu 12.04 and all the applications that I use), so I attempted to install xfce4. When I issued the command

sudo apt-get install xfce4

I was told that there where pending installs and that I should run the command

sudo apt-get -f install

before installing anything.

I ran that command and noticed that there where a bunch of Linux Image headers 3.x installing. I rebooted to see if this fixed the problem - no dice. So, I pulled up another terminal (with Crtl+Alt+T after logging in) and installed xfec4, then logged out.

When I logged into the xfce 4 desktop environment, I was presented with the same message about the unity greeter having closed unexpectedly, but was able to use the VM.

I know that I'm being pretty vague here, and I apologise for that. Is there a way to "fix" Ubuntu 12.10 on my VM, or to rollback to 12.04?

Note: I'd have pasted the entire log, but I'm having trouble bringing another terminal up after logging on.