Is my card too hot?

[Unreal89]

I ran 3dmark03 and after about 2-3 sec of 1st game my pc goes to a black screen. I have a 9500pro V-modded (dunno the voltage cause the zalman heatsink is in the way), it should be around 1.7V. I ran 3dmark03 at 385/303. At stock it runs fine. Is it heat, or not enough voltage? I would think that its not enough volts because overheating gives artifacts, not a black screen. Isn't it voltages that cause instability and crash the game. I'm sorry, but I am very knew to this stuff, yet I am very intrested. I love the thing you guys do, and hopefully you can guide me :)

thanks