Whenever I try to add images with the new 1.9.0 next-gen gallery update recently I get a HTTP 500 error on the pictures. When I disable Role Scoper everything works fine. (with all plugins disabled and just using role scoper, it still breaks.)
Just a heads up. Will have to downgrade til a fix comes out I hope! Great job your doing, keep it up the plugin is awesome.
I notified next-gen gallery developer on the forums also.