Media Library Image thumbs not appearing when adding new post

Hi,

Today I was importing files from another sites, and I forgot that you cannot simply take uploads from one site and move them to another. Well, this somehow messed up my uploads on edit pages. When I click the Upload Image button and then click on the Media Library option, none of the image previews are being displayed, even though it shows how many images are in the database. How can I get this fixed? Here is an image to show you what I mean.

Here is the image

Your help would really be appreciated!