[Plugin: WordPress Link Directory] “Not Found” /?cat=Automotive is not working

It was working, but for some reason now when I click any of the categories I get “Not Found

Sorry, but you are looking for something that isn’t here.”

Any ideas?

I have not dropped the table, but have reinstalled it. I can add links and categories, but when you click on then, you get the above message.

http://wordpress.org/extend/plugins/wordpress-link-directory/