JPRT runs SPECjbb2005 tests to qualify the JVM. At the end of the test, reports are generated which interact with SystemUIServer. Likely because of this interaction, the tests intermittently hang perhaps indefinitely and/or timeout. Until this problem can be resolved on Mac OS X, these tests can be commented out. However, the JVM integrations will be unable to fully smoketest.

The SPECjbb2005 software is available at /java/devtools/bundles/share/tests/jbb.tar.gz. I've attached a quick personal script I use to choose JDKs and run jbb with JPRT options.
Run this script locally on the Mac and you will see an occasional "JBBMain" window popup and disappear.