I agree that the new card might be defective, but it could also be a problem with your power supply or connections. I suggest you try as many variables as you have available before rma'ing the card. Did you turn the monitor off, then back on before trying the new card? You might try using both of the adapters that came with the card (molex to 6 pin) rather than the psu 6 pin + molex adapter. You could also clean the gold contacts inside the pcie slot with a q-tip and alcohol, then make certain the card is seated completely inside the slot... maybe even reseat the card a few times, and test it without the expansion slot screw inserted; the screw, when tightened, might be pulling the card away from the gold contacts. Exhaust all your possibilities before returning the card as defective.