Maybe time to start reinstalling windows mate if you don't have another pc to test the card on, it will save you the headaches and time to try troubleshooting it, it could be a bad registry in windows causing the problem too.
Time to backup all you need on the OS drive and reinstall I think that is your best bet mate. I can't see the card being borked but a borked windows install sounds more likely to me. RMA is not cheap to send out such cards insured remember. So worth trying a reinstall before that and if you have a spare hard drive maybe try install the OS on that as a test quickly to confirm the card is faulty and not the windows install you have currently causing you the problems.
Good advice.