categories pages disappeared after updating wordpress to 2.8

[digital]

The subcategories that used to be there now come up 404 ie: http://www.jessicaalba-is-hot.com/media/wallpaper/ used to display all posts in wallpaper, wallpaper being a sub cat of media, now it comes up 404, all the cats show in admin etc, if I go to url : http://www.jessicaalba-is-hot.com/wallpaper/ it displays all the posts in wallpaper, but if I use the top menu or browser and try and access the url from the main cat it goes 404. And all sub cats are now 404. :x

website: http://www.jessicaalba-is-hot.com/