Graphic Cards Graphic card overheating!!

[Homer]

Hey folks,i've got this wierd problem lately.Everytime I go to play a 3d game the PC shutsdown 3min in the game.For eg,i'm trying to play Prey.The game starts fine ,i can change the settings in the menus and all.But when I go to play the game after 2 -3 min the PC just shuts down.Is this because of weather (being so hot and all..)or is it the problem of the card.Like I said it only happens when playing a game,is the card overheating or is it the CPU.
Also i've opened the side of my cabinet and while playing prey the card only feels warm.(Avg temp is around 50C of the card when idle)
What do you guys think ???????

 

[DCEite]

what card you have?

 

[biosbhai]

Its your PSU I think. It cant seem to handle the load.

What is your PSU?

Post detailed configuration please.

 

[thexfactor]

use rivatuner to check the temps when you are gaming , else it may be the psu

 

[Homer]

My card is a GeForce 6800GS.
Config is
AMD 64 3000+
1GB ram
PSU is a Powersafe 400W.

But i've never had a problem before.I've even overclocked the card while Carbon ,Quake 4 and not once faced any problem.
Also for light 3d games like DaveMirraBMX -no problem.It's only when I play high res 3D games.Any solutions.I'm getting really bored not being able to play any good games.

 

[cranky]

Will you do me a favor and run a single loop of Memtest on that 1GB stick?