Corrupt DirectX graphics, with Radeon X1600

Hi all,

I've just installed Sid Meier's Railroads and the game runs but there's this
odd corrupt bit at the bottom:
http://www.fortawesome.co.uk/media/Railroads.jpg

I haven't tried many games but I also get this on the Windows image
slideshow if I change to one of the fancy styles (Collage, etc.) so it's
something to do with Direct3D. But the Windows interface itself is fine, no
problems. Anyone else had this?

Nick