Jay Ashworth reported a problem that arose between 1.7.6 and 1.7.7. His example used Swing events and requires manual clicking to use. I've reduced it to a simple test case (although not in JUnit form).
The interesting thing is that it takes two levels of Runnable inner classes for the problem to show up. Turns out threads are not part of the issue.
Demo script attached. The output for Groovy 1.7.10 is:
Caught: java.lang.NoSuchMethodError: TestInnerRefs$2.this$dist$invoke$2(Ljava/lang/String;Ljava/lang/Object;)Ljava/lang/Object;