can't get a ff extension to work in v3.0.5

Does anyone know what might have changed since v3.0.5 that would enable extensions to work? Or, maybe I'm missing a setting somewhere? I wrote this add-on that works fine with newer versions, but I can't get it to launch in older ones. Specifically, I can't even get this part to work (this is in my browser overlay.xul):

<html:script>
<![CDATA[

    var Cc = Components.classes;
    var Ci = Components.interfaces;
    var obSvc = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverServic开发者_C百科e);

    gBrowser.consoleService = Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService);
    gBrowser.log = function(msg){
        this.consoleService.logStringMessage(msg);
    }

    gBrowser.newObj= new MyAddOn();
    gBrowser.log("initializing...");
    function regListener()
    {
        obSvc.addObserver(gBrowser.newObj, "http-on-modify-request", false);
    }
    function unregListener()
    {
        obSvc.removeObserver(gBrowser.newObj, "http-on-modify-request");
    }

    window.addEventListener("load", regListener, false);
    window.addEventListener("unload", unregListener, false);

]]>

This should attach listeners to the new obj (defined by a linked .js) However, I'm not even getting the "initializing..." message in the console. Any ideas?

1. Don't use <html:script>, use <script> (assuming you have xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" on your root <overlay> element).
2. Don't register an application-global listener (http-on-modify-request) from a window overlay. Doing so will make your code run one time in each window the user may have open. Use an XPCOM component instead - https://developer.mozilla.org/en/Setting_HTTP_request_headers
3. Don't pollute common objects (like gBrowser or the global object (with var Cc)) with your own properties. If everyone did that, no two extensions would work together. Put all your code properties on your own object with a unique name.
   • accessing gBrowser before the load event is probably what's causing your specific problem.
4. Set up your environment and check the Error Console to debug problems.
5. Don't waste time trying to support Firefox 3. It's not supported by Mozilla itself for over a year and shouldn't be used to access the web.

It looks like gBrowser.log is not defined, or at least is not a function, as the error console will probably tell you. I've never heard of it either. Maybe it was added in Fx 3.5?