I've got the exact same problem here, only there are two parallel flickering stripes with the same width as yours. The lid's also being slightly pushed away on one side in the very same way yours is. And the MB is 18 months old, warranty has expired and the mac store guy only suggested trying to sound pitiful on the Apple hotline, which will probably not work.
Maybe our problem is related to the following one, sounds very much alike? http://www.ifixit.com/Answers/View/9868/display+shows+purple+strips