I agree with the last answer, except he should have told you first power down, unplug your system, and pull your video card back out and put it back in again to make good contact. If you have more than one slot compatible with your card, you can try the other one. That works 95% of the time. Please don't forget to blow off your motherboard before replacing your card again. It is very likely that some dirt or hair could be interfering with the cards contact. Also, if you were touching any of the contact points while handling the video card, wipe them off too. Once your card is back in, and the 'correct power' from your power supply is hooked to the card, boot up. If the problem is the same, then reinstall the nvidia driver. If that doesn't help and you have changed slots if applicable, your card is damaged.
My source is that I am a CompTia A+ Certified PC Specialist.