What is going wrong with ggts 3.6.3 on linux (e.g. broken code completion, compile errors)?

Question

I downloaded GGTS 3.6.3, extracted, and ran it on Ubuntu 14.10.

I tried importing an existing grails project and when that failed, I created a new workspace and a new grails project ("test"), inside of which I created a single controller ("test").

Basically nothing works. For example, when I try to write a simple line like import java.util.HashSet, the UI crashes to a halt and code completion fails with:

Or when I type a line like import java.util.HashSet code manually (without code completion) I see various compile errors appear in eclipse's stdout like:

/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:unable to resolve class java.util
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:unable to resolve class java.util
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:unable to resolve class java.util.Ha
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.
/test/grails-app/controllers/test/TestController.groovy: 3 Groovy:Invalid import  @ line 3, column 8.

But while the error appears in an individual file in eclipse:

... there's no summary view showing me all of the errors. That is, eclipse's "Problems" tab is blank:

In short, I can't accomplish even the simplest tasks in a fresh project, let alone actually opening my existing project. Is anyone else experiencing these issues?