add:  var aus = Components.classes["@mozilla.org/updates/update-service;1"]. getService(Components.interfaces.nsIApplicationUpdateService); var checkNowButton = document.getElementById("checkNowButton"); checkNowButton.disabled = !aus.canUpdate;  
context:   updateAppUpdateUI: function ()  {    var preference = document.getElementById("app.update.enabled");    document.getElementById("enableAutoInstall").disabled = !preference.value;    this.updateAutoInstallUI();    return undefined;  },
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/304cbe853b4ea51a95b2815c55ef9d2a50c0dffb/advanced.js/clean/browser/components/preferences/advanced.js