I have a google Layer map on top of which I have added a raster layer of Image and then mapped image coordinates from Google layer.

I made transparent (75%) image map layer and now mapping and creating polygons on top of image layer (Added new shapefile layer)
I drew few polygons and then saved it.

When I reopened the file, clicked on toggle editing, I could see my polygons, but I am not able to add/edit/delete existing/new polygons in that shapefile layer. (All icons are disabled)

Is this expected behavior?

My old question on what exactly am I doing.
http://gis.stackexchange.com/questions/144848/how-to-create-obtain-district-data-for-singapore