I have tried to protect images with the plugin using WP 3.0 and NGG 1.70a. The image is only hidden but if a person has the specific URL to an image is still shows so the plugin is useless :(
Would it be possible to protect the images with a real .htaccess control, so it is not possible to deep link (using the real URL) to protect the images?
http://wordpress.org/extend/plugins/user-access-manager-nextgen-gallery-extension/