Did you uninstall any old driver(s) before installing the latest AMD driver for that card and OS?
You may want to try this. Uninstall the driver again and run Driver Sweeper from safe mode. This version: http://www.techspot.com/downloads/4266-driver-sweeper.html
Have it remove any remnants of old AMD, Nvidia, and ATI drivers it finds. Reboot and install the latest driver for your card and OS. http://support.amd.com/en-us/download