I had this problem once, I resolved it by fixing my /etc/fstab file which had incorrectly set my /home drive. But as you mentioned, it's a single partition. I also once resolved it by reinstalling the ubuntu-desktop package.
This issue is fairly wide-spread throughout the Ubuntu community. There are several other users who have had this issue and the various resolutions seem to point towards some sort of issue with either the graphics card drivers, Unity, or Compiz.
A point of confusion however is the difference between blank screen and black screen.
Here's a "blank" screen problem:
In this scenario, a user has a problem similar to the one you described: A blank screen when they attempt to login. This is different however due to the fact that they are using a physical computer as opposed to a virtual machine and also because they are not returned to the login prompt after a short delay.
The problem was resolved when the user reinstalled Ubuntu without checking the "Install third-party proprietary software" box at install, preventing the Nvidia drivers from being installed.
Here's another blank screen error. This one is a bit more similar to your problem since it's a virtual machine.
The problem that the asker had was that after installing 12.10, when they attempted to login it would go straight to a blank screen:
Ubuntu 12.10 desktop/interface not showing on VirtualBox VM after login screen
It was apparently resolved by using Gnome Classic.
What I actually suggest you do first is that you install or update the VMware Tools.
This site provides instructions on how to install VMware tools on an Ubuntu virtual machine.
If that doesn't work, I would suggest is that you try reinstalling Compiz.
How can I remove and re-install Unity?
This worked for me, so I hope it will work for you as well. I've heard this can be caused by a great number of issues, so I sincerely wish you the best of luck.