FPS Problem with Radeon 5850

My friend is having serious issues with her graphics card. A while back, her motherboard died on her, and she ended up having to replace it with a new one. Prior to this she had no issues with her 5850. It ran all of her games fine. Now, she is getting low FPS in Guild Wars 2. She also got low FPS in Final Fantasy XIV 1.0 and the alpha version.

She's tried completely uninstalling and re-installing her drivers and that does work. But whenever she puts her computer to sleep or turns it off, the problem comes back when she turns the computer back on. FPS numbers are sporadic and all over the place for a while, and then they drop down to less than 10 FPS in GW2. So now she has to either keep re-installing her drivers or leave her computer on all the time. Any hints as to a solution to this?

Her current setup is:

i7-3770K cpu
ASUS Sabertooth Z77 motherboard
ATI 5850 HD graphics card
16 gb RAM

I want to reiterate that we've completely cleaned the system of drivers used driver sweeper and re-installed the latest ones. Each time it fixes the problem UNTIL the computer is turned off or goes into sleep mode. Then her FPS drops hard and stays that way until drivers are re-installed again.