Dell Precision M6500 GPU or LCD dying?!

Hi there!

I have a Dell Prec. M6500 laptop.Specs: i5 580m ,4gigs ram, Quadro FX 2800M.
This is the problem:  https://www.youtube.com/watch?v=eDjFIjx183A

I can't really describe the situation well ,but let the video speak for itself. I had problems with strange artifacts,blank screen and such ,but undeclocking the gpu and some light slaps under the screen(no joke) always solved them.This particular phenomenon which I'm dealing with has started after a  3minute stress test on the gpu with FurMark(I wanted to see the temps so I could decide if a thermal paste replacement and heatsink cleaning is due or not).I disassembled the laptop ,replaced thermal place ,reseated cpu and gpu AAAND IT WORKS!!Or at least worked for a minute or two ,then started to do the same thing that is in the video.Any ideas what could be the solution?Maybe a new cable to the screen could solve it?New GPU? Or should I just sell it as faulty laptop or parts and move on? Honestly I really love this machine ,even though it is a pain in the *** to carry around and I can't really use the GPU because I get blank screened.Feel free to write a comment ,even if you just want to tell I'm a retard or something.You guys really didn't help me with my other post ,but hopefully someone cares and knows something I don't.

Thanks in advance.