When I run your app with Firebug enabled I see 'Aborted' errors due to this layer. Do you have an updated version of the app?
http://www.gisprod2.com/ArcGIS/rest/services/Dynamic/Zoning/MapServer?f=json&dpi=96&transparent=true...
In your app it looks like you setup the listener for the maps onLoad event but you don't have a mapReady function in your app.
dojo.connect(map, "onLoad", mapReady);
The basemap gallery should be created once the map has loaded so try adding the logic in the mapReady function and it should work.
function mapReady(){
createBasemapGallery();
}
Uncaught ReferenceError: dojo is not defined findGrid.js:1 Uncaught ReferenceError: dojo is not defined identify.js:1 Uncaught ReferenceError: dojo is not defined index.html:27