Gtk: Choicebox and Advanced Stage samples cause jvm to crash

When making a choice from a choicebox button java crashes. Also, selecting the close me button for the advanced stage sample will cause crash, only reproducible on Ubuntu.

To reproduce:
Launch Ensemble and navigate to ChoiceBox sample
Make a selection from the choice box and Ensemble crashes.

#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x0118e431, pid=1399, tid=2699787120
#
# JRE version: 7.0-b148
# Java VM: Java HotSpot(TM) Client VM (21.0-b18 mixed mode linux-x86 )
# Problematic frame:
# V [libjvm.so+0x268431] jni_invoke_nonstatic(JNIEnv_*, JavaValue*, _jobject*, JNICallType, _jmethodID*, JNI_ArgumentPusher*, Thread*)+0x161
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/uadmin/Downloads/javafx-sdk2.1.0-beta/javafx-samples-2.1.0-beta/hs_err_pid1399.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
#
Aborted