Wanted: Thread help

Assumption: this is pretty classic situation.
Assumption: this crash is due to threadA (triggered by jit.notify) and treadB (triggered by bang) attempting to access the same jit.render at the same time.

I spent all day toying around and trying things and researching threads (I'm a noob at that)

So I'm here to ask. Whats the best way to arrange things so this won't crash. In real life, This a UI like a step sequencer. So the jitter notifiable is like me editing it with a mouse (quicker), and the bangs are like the clock causing a line to go across it(slower).

I was hoping to avoid repeatedly rendering al a qmetro because:
A, it would look choppy when using it as a UI object
B, it would be cpu intensive for times when I'm not using it.

Steps to crash,
instantiate mxj TestDrawCrash
hook a metro up to it,
drag around the jit.window

import com.cycling74.jitter.*;
import com.cycling74.max.*;
public class TestDrawCrash extends MaxObject  implements JitterNotifiable{

    JitterListener myListener;
    String name = "IwillCrash";
    CrashWindow cw; 

    public void notify (JitterEvent e){
        cw.draw();
    }

    public void bang(){
        cw.draw();
    }

    public TestDrawCrash(){
        myListener = new JitterListener(name,this);
        cw= new CrashWindow(name,300,300 );
    }

    class CrashWindow  {
        JitterObject myWindow;
        JitterObject myRender;
        String name;

        public CrashWindow(String name, int width, int height) {
            myRender = new JitterObject("jit.gl.render", name);
            myWindow = new JitterObject("jit.window", name);
            myWindow.setAttr("size", new Atom[] { Atom.newAtom(width),Atom.newAtom(height) });
            myWindow.setAttr("pos",new Atom[] { Atom.newAtom(0), Atom.newAtom(800) });
            myWindow.call("front");
            this.name = name; 

        }

        public void draw() {
                myRender.call("erase");
                myRender.call("drawclients");
                myRender.call("swap");
        }

    }
}