I moved a stand-alone WP blog over to a WPMU install. Everything looks fine - except none of the images show up. The uploads folder from the old blog was moved over - and everything is in the correct path. A new image uploaded from the blog appears alongside the 'old' images. But - when you try to load the image in a browser you get a 500 internal server error.
Also - none of the 'old' images show up in the media library in the admin. So - where is that controlled and why does the direct path to an image not work.