It could be a faulty card, as you have mentioned, it would overheat often and might have damaged some of the components , possibly the display ram. If the drivers indeed have mixed versions, you can make use of Driver Fusion >

to remove and clean old drivers.
Re-install the card with latest driver then download and do a burn-in test with these utilities:
FurmarkGPU Shark (for monitoring the card)
Keep an eye on the temperature and fan speed, post results when done.