various

1 - why can't visitors see the categories on the website? If i'm logged in i can access categories and click links. Visitor, i can see the taxonomies, but not the associated categories

2. - how can i modify the thumbnail sizes in both the category listings and the listing itself?

3. - what happened to the featured image box for posts? i'm installing NIVO slider plugin and it needs featured images from posts to show the images.

This is for the directory plugin.