It al depends on whether you are meaning black lines are seen on the the LCD over whatever the lens is pointing at, or that this occurs only on playback? If its the former, then try coupling the camcorders A/V output into your TV and observe if the lines are still seen and if not then the LCD is likely faulty, but should they still be there then an internal fault is liable to have developed, the image sensor being the prime suspect. If however lines are only seen on playback then the video heads are likely to require cleaning, you could try using a cleaning tape although wet cleaning is always much better, although unfortunately the procedure used to "safely" do this can only be sent to a direct e-mail address as it contains a jpeg attachment for illustration purposes.