Laptop (ASUS A43S) screen turns black, then restarts 10s after starting game?

Hi, 2 nights ago I was playing a graphics intensive game when my 2 year old laptop screen suddenly went black and then restarted itself. I thought it was the usual static/black screen error so I proceeded to do this:

1)unplug laptop and removed the battery

2)press on the power button for 15 secs

3) let the computer cool for 1 hour

4)start the laptop

However, 5 seconds after I opened the game, my laptop screen turned black and restarted itself. However, now my laptop became noticeably slower. I then tried opening a web browser to seek an explanation an fill in an RMA. But 5 minutes later my screen went black and restarted again. This would keep occuring whenever I tried again.

However, I noticed that if I leave my laptop on but idle with no programs running, nothing will happen and everything seems normal.

I then downloaded the newest Nvidia driver, but the same thing happened to me (black screen then restart when 10s into game, 5 mins into browser, nothing if idle)

I then proceeded to disable my Nvidia graphics card, and something even more alarming happened: 1 minute after I disabled the graphics card, my screen would freeze, turn white but you could still hear the normal functioning sounds. I can't remember if the computer would crash after this.

I think I should mention here that I just had my computer sent in and repaired 3 weeks ago for the same frozen screen turns white problem + a loose power jack repair. When I received the laptop back they said the entire screen was replaced but I though I could sometimes see 1 or 2 black lines on the screen sometimes. However this really happened too rarely for me to care.

I also use my computer for extended hours, sometimes up to 10 hours a day non stop. If it is relevant the day my problems cropped up, it was a particularly warm summer day (25 degrees celcius, i'm from UK)

My laptop is an ASUS A43S with GT540M graphics card, and it has and i7 2430QM processor. My hard disk was replaced in January after a slew of BSOD problems, but that has not happened again. I have had power jack repairs twice, once last summer and once 3 weeks ago.

I can find no satisfactory answer to my plight on the internet, and was hoping you might help me out!

 

I hate to say it, but it sounds like the video card is on its way out (or at this point, has gone out). Does your system use switchable graphics (Optimus)? I know many Asus laptops don't, but not sure about your model.