MBP screen flashing black randomly

Hey guys

I have a 2.53Ghz MacBook Pro (Late 2009 so two GPUs). Everything on the system is great but after a few months the system started displaying a small but really annoying issue.

The screen randomly flashes black. Sometimes it is the whole screen or just a section of the screen but always most of it and all ways for edge to edge. So never just a small square, usually 2/3 of the screen like about top 2/3 and the bottom 1/3 is normal. It only happens of a second and is gone again. It happens in no particular circumstances.

The issue is small but really annoying when I am trying to get a photo right and I am focusing on a picture and bang black screen. I have taken it in for repair (under applecare) and will be again tomorrow. Last time they replaced the screen and logic board. They also tested the wireless card too. They said all was well. Now it has started doing it again. I figured it could be a HDD issue (unlikely) so I got an new HDD and did a fresh install but it is still present.

Any ideas what could be causing this? I think it is relatively simple issue like a transistor or something. Of course, the machine never does it in the shop.

Thanks

Mike

Could it be something wrong with the connection to the screen? On my old MB (granted, after a few screen replacements), the ribbon connecting the screen to the rest of the computer wore out, causing my backlight to flicker on and off. I'm guessing the same thing might be happening, which would explain why only part of the screen is shorting.