Method TestPanel.stop() stops secondary thread and waits for the moment it is finished using Thread.wait():

    public void stop() {
        active = false;
        try {
            synchronized (sync) {
                sync.notify();
            }
            synchronized (thread) {
                thread.wait();
            }
        } catch (InterruptedException ex) {
        }
    }

Usually system 'notify' occurs for that wait() and the test exits normally, but on some machines (i.e. stt-96-vmw5) it doesn't happen and the test gets frozen.
To resolve this issue 'waiting' code should be rewritten to guarantee the notification of thread's finishing.