This video describes pretty same problem: http://www.youtube.com/watch?v=3QpNl42RO6c According to comments, this bug can be induced 1. By dirt on the back side of the touch screen 2. By broken digitizer So, please tell me. I got to go to the service center or i got to try cleaning up the screen? If someone already cleaned up screen, please give me some links on good manuals.