Hi... tried the Edit Categories link in the admin section > Edit > find "These checked usergroups can view images in this category" and uncheck the box marked 'Unregistered / Not Logged in' (or whatever the user-group name you have) do this for every category you have, for comments i wouldn't know for sure...good luck
Hmm, that is very strange. I only have two categories checked in order to be able to view images and "unregistered" is not one of them. I have ADMIN and REGISTEERED users only being able to see the "comments" section. However, unregistered persons can still see the comments and the thumbnail's of the pictures.