Hi kagome_angel,
I would suggest you to please remove the Previews File of the Catalog, it will be in the same location of the Catalog, and will be <Lightroom Catalog Name> Previews.lrdata.
Please make sure Lightroom is closed while you are renaming or deleting this file, and then open Lightroom and see if it works.
In case the above does not help, please try and check the Monitor Profile of the computer : http://www.lightroomqueen.com/articles-page/how-do-i-change-my-monitor-profile-to-check-wh ether-its-corrupted/
Regards,
Tanuj