I can't speak for v2 of the CMS product but v1 of PowerCMS and v2 of PowerGallery cannot use the same interface. They have seperate WA_Globals files (which contain the passwords) and they also have their own directories. You can probably do it if you have SecurityAssist but I haven't heard of anyone doing this. I just set my site up with the login from seperate items on the Administration menu. One for content and one for the gallery.