Cannot add custom fields to posts -ajax not working

Hi all,
I’m trying to add a new custom field to use the “articles” plugin in one of my blogs (www.secretia.com) and I noticed the custom fields applet is not working in my write/edit post page. The list of fields is not appearing over the deployable menu with the existing fields and when I try to add nothing happens. When I try to save the post after adding the field it just asks me if I’m sure to want to leave the page and that’s it… I really need to fix this! Any suggestions? I’m using WP 2.1

PS: Almost the same happened in another of my blogs (www.jewishculturela.org) but this one says “you don’t have permission to do that” when I try to work with custom fields in it. It was doing the same with categories until I added the Category Manager Plugin. Now when it’s on it allows me to create new categories but wp lists them all together as several categories with one same long name containing all the categories’ names.