gBrowser.addEventListener: "load" event fired three times

Question

Hi,

I have installed the "hello world" dev example for Firefox extensions as described here: http://blog.mozilla.com/addons/2009/01/28/how-to-develop-a-firefox-extension/

I have modified the anonymous function that gets passed to gBrowser.addEventListener:

gBrowser.addEventListener("load", function (event) {

    var t = event.target;
    alert("Content title: " + t.contentTitle);          

}, false);

This function is getting called three times for every page load. When I click a link, it fires twice for the current (already loaded page) and once for the new page.

I have uninstalled all other addons (including Firebug) and still it fires 3 times. Does anyone know why this might be?

Thanks Richard