Not Found Error Category

Greetings to all:

Can someone please tell me why I get this message error and how to correct it? Not Found – The requested URL /wordpresscategory/movies was not found on this server. When I click on a category it defaults to: http://mysite/wordpresscategory/categoryname. I am using the “News Magazine Theme 640”

URL: http://associatedepress.org/wordpress

I spent several hours trying to figure out where the “wordpresscategory” might be to no avail and I kindly request anyone’s assistance in this issue. Please help. I am desperate.

Thank very much for your help.

Best regards.