Error Starting Ubuntu Desktop on Chromebook After Upgrade

As I've mentioned in previous posts, I'm very pleased with the Toshiba Chromebook I picked up last year. Like many Chromebook users, I decided to install Crouton and have access to a full install of Ubuntu Linux. I followed the instructions in the article How to Easily Install Ubuntu on Chromebook with Crouton and all went smoothly. Switching between Chrome O/S and Ubuntu is as easy as a key combination--you just have to remember those keys: ctrl+shift+alt+forward (or backward).

Unfortunately, the version of Ubuntu installed was 12. As fun and nostalgic as that was, I immediately set about upgrading to the latest stable build. Running the upgrade was simple enough.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get install update-manager-core
sudo do-release-upgrade

Everything worked at first, I even went through the process of installing some applications such as Gnome Terminal, Gimp and Git (Crouton installs the minimal release--so barely any applications). However, I ran into a snag when I rebooted. The sudo startunity command would fail with a nasty message.

...
[   727.514] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist.
[   727.514] Entry deleted from font path.
[   727.514] (==) FontPath set to:
/usr/share/fonts/X11/misc,
/usr/share/fonts/X11/Type1,
built-ins
...
727.526] (EE) Segmentation fault at address 0x0
[   727.526] (EE) 
Fatal server error:
[   727.526] (EE) Caught signal 11 (Segmentation fault). Server aborting
...
[   727.526] (EE) Please also check the log file at "/tmp/Xorg.crouton.1.log" for additional information.
[   727.527] (EE) 

I prefer the Unity desktop, so that's the one I had originally installed. To work around the error, I reinstalled Unity using the same command in the original setup article:

sudo sh ~/Downloads/crouton -t unity.

To be clear, this simply reinstalls the desktop. I still had the latest version of Ubuntu and the applications I had installed after running the Crouton install.