OK....so the XPCSafeJSObjectWrapper.cpp (line 445) is a red herring?
I restarted Firefox (yes Firefox 3)...but the code doesn't call the PHP. I'm watching the webserver logs where the PHP is hosted and not getting any hits when I refresh the login page.
I've added the appropriate RSS Ticker code to login.jsp....
I think that path to the rssticker.js is correct as it's appearing in the Script tab in Firebug.
MORE STUFF HERE
Is Zimbra preventing the script from calling out to the external webserver with the error...
Access to restricted URI denied" code: "1012