http://java.net/jira/browse/MACOSX_PORT-134 submitted 2011/07/01 by Yuri Nesterenko
If System preferences for the Energy Saver is set to Display sleep == certain value which is not Never, and if that timeout reached, then Java programs starting after this moment bomb in Window.initGC() presumably having null default screen device.
gc = GraphicsEnvironment.getLocalGraphicsEnvironment().
Actual situation like this is a long Swing test run: if a test fails with timeout, most subsequent tests fail in Window.initGC().
Now, I don't know if it is possible to fix this in the program. Is there a way on Mac to provide a default Screen device without a monitor attached?