ERROR: JDWP Unable to get JNI 1.2 environment
Just add System.exit(0); to the end of your main method.
That's all you have to do.
Looks like http://bugs.sun.com/view_bug.do?bug_id=6476706 which has low priority and is still not fixed. Definitely a Mustang bug but no clear explanation (seems to occur pretty randomly according to the bug reporters on top of that).