did you uninstall your cat 4.7s before you installed your beta 4.9s? Did you run driver cleaner before installing the beta 4.9s?
Here, do these two things.
First , download this:
http://mirror.ati.com/support/drivers/misc/catalystutils.html
Download the Catalyst uninstaller. It removes your current ATI drivers.
Second, download this:
http://www.driverheaven.net/cleaner/
This is driver cleaner. After you uninstall your ATI drivers, reboot into safe mode and run this program. It'll get rid of any lingering files. Follow the directions on the webpage. Then you reboot back into windows and install the beta 4.9s.