NextGen Gallery Album Preview Image Trouble

In nextGen gallery, I am unable to select a preview image for the album field.
Under the field where it says: “select a preview image” I have no idea what to do. I’ve noticed that other people have had similar problems, but they usually have at least SOME option of a dropdown field- where as for me, there simply is no drop down field available when I click on it (although I am well aware that there is plenty of images from galleries uploaded). Also- I cannot search for an image. I try typing something in- and on the right hand side a loading icon appears- but nothing happens. There is nothing I can do to my knowledge.

Here is an example of the problem: http://komicks.com/?page_id=1660

The albums Uncommon Sense and EVERYTHING ELSE do not have preview images but they have galleries in them. (the others listed there are galleries so they have previews)

I greatly appreciate any help- thank you!

I have firefox 3.6 and I am on a Mac OS