Hi Sean,
A HeadlessException happens when the java.awt package tries to ask the native X11 server to display components, but the X11 server returns that it is headless, i.e. has no display.
https://www.ibm.com/developerworks/community/blogs/738b7897-cd38-4f24-9f05-48dd69116837/entry/how_to_resolve_java_exceptions_java_awt_headlessexception7?lang=enUnfortunately, what you're coming up against is a machine specific error that I can't replicate on my 64-bit Ubuntu machine, so I'm a bit limited in how I can help. However there are a few things you can check and see if it clears up the problem.
http://stackoverflow.com/questions/18099614/java-lang-noclassdeffounderror-could-not-initialize-class-java-awt-toolkitThis person had a similar problem, which they solved by installing libxtst6:i386... seeing as how that's a 32-bit library, it looks like they might have also been running a 32 bit JRE on a 64 bit machine. So you could try installing libxtst6:i386 or you could make sure that your java is also 64 bit.
Lastly, based on the first link, you could look into your Xorg server and make sure its not telling Java that its headless for whatever reason. This could be in the settings or Xorg could be improperly installed... I couldn't say for sure.
Hope this helps!