Q: I have a Sony Vaio PCG-GRV616G and Sony Vaio Laptop GRX570 with the same problem.
The photo of the flickering screen is here: http://yurradnik.com.ua/img/screen.jpg

First, screen went to the "flickering mode" after the hours of work, usually after 6-8 hours of work.
Now screen goes to the "flickering mode" immediatly.

I noticed, when I run heavy-loading graphic application (some 3d demo or video, all in full screen) for 3-5 minutes and then restart the laptop, "flickering mode" disapears. "Normal mode" can lasts from several minutes to several hours. Then "flickering mode" comes again.

Any ideas, please... 

A: You have a problem from a video chip of your laptop . Although both of your chips are different ATI chips, the end result is the same. It's Video RAM related and is usually only repairable by replacing the video processor. With this being said,  we do offer this repair but it's longer term reliability is limited, the better do that replace a motherboard to your laptop.