Run a driver sweeper to clean out all of the old and new drivers. Then reinstall the drivers and make sure you do a clean install. When installing you will come to a choice to choose from.
Recomended or custom choose custom and then click on clean install. Now after you doing all that and nothing works then try your card in someons eles rig. To see if you get the same problem.
Here is a driver sweeper. Try this and see if it will work.http://www.guru3d.com/category/driversweeper/