If there is one thing I never really liked buying off eBay were computer parts. They could have been overclocked without proper cooling, stored in wrong places, not properly handled, etc.
But anyway, I'd recommend you a few things:
- Make sure the card is getting enough cooling. Even fanless cards almost require at very least a case fan near it. I have a 8600 fanless card and it was highly recommended to have a case fan:
SYSTEM FAN in chassis is recommended for using the Silent graphics card. For the best heat dissipating results, please place the PC in a location with good ventilation.
And my card is pretty bad, especially when compared to both your cards
. So cooling is important here.
- Make sure the card is getting enough power. Nvidia cards are getting more and more needy. Make sure your Power Supply is up to the task;
- Test with another driver, even if older. Sometimes new drivers can have some bugs like that.
Good luck there mate!