Video help needed

I just built a new system with the following components:

Intel E8400
Gigabtye GA ep45 ud3p
4 G Ram
Windows Xp SP3
HIS 4850 512 256bit
Antec Sonata 3 w/ 500 watt power supply

When running 3DMark05 or Sandra video benchmarks, I get a blank screen. The computer fans keep running but the computer is not responsive is not sending a video signal. I am able to play DVDs and I successfully ran DXDIAG test. I've tested the CPU and the RAM and both appear to be fine. Any ideas on what the problem might be? I've tried 2 versions of the ATI drivers and have Directx 9.0c installed.

Thanks

Don

 

Perhaps the card is overheating and shut off to prevent damage. Check the idle temp of the GPU.

 

Try RivaTuner and see what happens, imo by far the best test tool for gpu's
http://majorgeeks.com/Riva_Tuner_d737.html

 

Thanks for the replies, I'll checkout Riva tuner tonight.

 

This is a followup to the questions I asked last week. Turns out the power supply was the problem. I had an Antec Earthwatt 500W PSU which I replaced with a Corsair 650W and now my problem is solved. Not sure if the Antec PSU is just not strong enough or if it is defective. Anyway thanks for the help. Don