Vertical lines on laptop screen

I have a Dell Inspiron 6400, and about a year ago I sent it into Dell and had my LCD screen replaced for a pixel issue. Soon after I started to get colored vertical lines that prevent me from using the screen (my warranty has run up and it has been so long I cannot send it back to Dell). The screen looks very similar to this screen: http://www.asklaptopfreak.com/wp-images/color-lines-on-lsd-screen.jpg

When I hook the computer up to a monitor or even a projector I can see everything and use the computer fine, the screen remains unusable with the vertical lines though. I put the laptop aside for a few months because I had no idea how to fix it. Randomly I turned the lap top on and it worked perfectly, no lines and no problems. After about a month the computer suddenly washed out and the lines appeared. Saddened, I again put the computer aside for a few months. About three weeks ago I tried to use it again and it worked perfectly but tonight it has washed out and the lines again appeared. I'm wondering if I need a new LCD screen or if it is simply a connection issue since the screen works fine sometimes. I appreciate any help or advice. If anyone has a step by step guide on how to fix a connection issue I would love that. Thanks