Thanks, tried that but it won't let me force the installation of the older driver, I get an error telling me I have broken packages. However, when I check for broken packages there are none.
In the meantime I've been playing around with the Nouveau driver. It's a little buggy when using the desktop effects, often areas of the screen will go blank or corrupted, but turning off composite extensions has solved that problem. I have been surprised just how much more responsive the desktop has become by disabling all the effects so I may just live without them. As a test I fired up BZFlag and the graphics acceleration is excellent. So I think I'll wait for a new driver from Nvidia and hope that fixes the problem, or just stick with the Nouveau driver
As an aside to this, I also had a problem with the updated Flash Player, the colours were sort of reversed. I read that by turning off hardware acceleration in the flash player settings solved that problem, however I didn't bother to try that, but using the Nouveau driver has solved that problem too. Even with hardware acceleration enabled in Flash, the colours are all fine.