Hi Rhuddlan. I suspect the answer to this is on page 68 of the July issue of PCA.
"Version 9.0 of the DirectX API introduced 'floating point' pixel pipes." etc.
This is a fundamental change in graphics handling that probably won't be supported by any games for a while yet. This will also probably require new drivers for the graphics cards and perhaps is giving problems with some existing drivers.
All guesses, but it makes some sense to me.