ATI X700 Mobility screen corruption

I have an ATI x700 mobility in my laptop and everytime I come out of standby, or when I change from a low screen resolution to a higher screen resolution, the screen corrupts (not just a few odd colours or tearing but the whole screen goes grey with horizontal and vertical grey lines from edge to edge). Closing and reopening the lid resets the screen back to normal and starting up from a shutdown does not cause the corruption. I've had this problem in XP since the 6.4 mobility drivers; every release after that set had the problem. With XP I could remedy this by sticking with the 6.4 drivers, but now I have vista installed and all the vista drivers cause the problem. I know it's not a hardware problem because up until the 6.5 mobility drivers in xp I never had the problem. ATI must have added something new after 6.5 which they have added to each driver set since which causes the problem. Can anyone think what might cause the corruption or does anyone know how to fix it?