Not sure why, but have my suspicions which I won't bore you with, just something about the way the page is built.
The quick but slightly hackerish solution is to go to the pic you want,
1) view source (in firefox ctrl + u).
2) ctrl + f.
3) Paste this line into the find box:
<div id="media_item" style="background-image: url(http://media.tuara.com/gal/event/
4) copy the whole url (starts with http://, ends at jpg) ctrl + c
5) paste that into a new tab. There is your picture.
hopefully you don't want to copy stacks of images because it would be tedious using that method.