Here's one reason you should be able to log in as root:
I copied a couple of directories to my home/<name> dir while in su mode and rebooted before I chmod them to allow me to have access.
Now I can't boot the Ubuntu system. When I try to log in I get the following message:
"GDM could not write to your authorization file. This could mean that you are out of disk space or that your home directory could not be opened for writing. In any case, it is not possible to log in. Please contact your system administrator."

If I could log in as root I could attempt to fix this problem.

Is there any way I can access this system? I only set up one user.
And... it's a virtual machine running in vmware.

Thanks!

if you can su into root then you can login as root, or at least you should be able to

Start it in single user mode.

or run level 3

You can enable the root account by simply doing "sudo passwd root".

You also typically have to enable login to the GUI---the utility is "login manager" (or something like that).
BUT: Logging into the GUI as root is a REALLY bad idea.