Lcd screen has a red line on the screen

There is a loose connection on the FFC ( Ribbon Cable ) cable connecting the screen. They come loose frequently and mine used to be pain in the butt when i had it. This also occurred with the FFC cable to the CD Rom. Pop up the brown tab remove the cable and verify that all the connections are still good. Place the cable back in the connector and close it back up firmly and test it again. You can get a replacement ribbon cable for it and i am sure there are a number of repair videos for this on youtube.