Screen image get some squares or unclear text's

Hi to everyone,

Sorry for my english.

I have a Latitude e4200, with gma45 on onboard. The problem is the image on the screen get some lines or unclear square's wich is very unconfortable. When I select the text for example image become normal.

What is the problem, in chipset? or some conections? the screen is 100% ok 

I want to change the motherboard but first I want to be sure the problem is in it.

Thanks a lot for your help.