Graphics Card Shuts off during crysis

Specs:
3.0ghz duo core (at stock
4gb ddr2 dual channel ram
windows xp
500 watt power supply
EVGA Nvidia Geforce 9800 GT 512mb with the latest drivers

Anyway, I am having an issue with crysis. I can play the game, it is recommended I play it on high which I do, I get about 29-40 frames per second. I can play for about a half hour or so then the game goes blank my monitor shuts off (get "no signal" ) and then my computer freezes and I am forced to reboot.

I searched around and I am the only one who has had this issue. Is this an overheating issue? Should I run the game on lower settings even though I feel I shouldn't have too? Any possible solutions?

I see you specify a 500w power supply, just curious what brand/model it is. I know the card recommends a 400w PSU but 26A on the 12v rails. Just want to make sure it's getting enough juice. Also, Crysis will make any card cower to it's knees. It will heat up a card more than any other game. My first though is you have heating issues.

Questions:
1) do you have good case airflow? what is your fan setup?
2) how long have you had the card?
3) does it have the stock oem cooler? Im refering to the 1 slot cooler.
4) is this the OC version or just plain vanilla card?

Sounds like gpu overheating. Like WR2 said, check out your temps using gpuz. If you are running above 80-85'C when you are gaming I'd say its a heating issue. You can use GPUZ to run in the background and log to a file. So I would run it several times and monitor the temps and it consistantly keeps raising and shutting off around a certain value then you know its your gpu.

It is either over heating or under power. What psu do you have?

Got the same symptoms on my pc recently.

System seemed to be running fine for the past few weeks only recently the screens would just shut off.

AMD Phenom II 945
DFI LanParty JR 790GX
4Gb of Ram (with big chunky heatsinks)
Asus Radeon 4970 Dark Knight cooler
ThermalTake 750W QFan power supply
OCZ Vertex SSD
Two 120mm fans blowing air through and out the back of the case, so my computer should NEVER has over heating issues as I'm a nazi when it comes to keeping my systems cool.


Basically while playing Left 4 Dead, the screens would shut off, I would check my computer, the graphic card fan has stopped and 3 red lights have gone on. (part of the asus 4970)

Replaced graphic card with spare Radeon 2600, and same thing sort of happened when playing WoW. Screens went blank (graphic card fan stayed on). My brother was copying files at the time and there we continuing to copy even after the screens died.

Checked temp on hard ware components, and nothing felt hot to the touch. So it doesnt seem to be an over heating issue.

No over clocking either graphic card.

Case airflow is fine, I work on PCs all the time at work and have to make sure they can deal well in warm environments. My case has 2 fans at the front pushing through to the back, where there are vent holes and another fan sucking out. Not to mention holes at the side of the CPU and graphic card. (Of which I have covered up but made litte temp difference)

At peak noticed radeon 4870 was about 75deg Cel
the 2600 hit 57deg.

This was using the stress test program "OCCT" http://www.ocbase.com/perestroika_en/

Note, doing the GPU test in OCCT also caused the problem.

About to change graphic cards to NVidia 7950 to see what happens