Alert:Windows ATI Radeon 4870 video card / CS5 / CMYK / Problem

A bit of an obscure one this as I know clients with the above graphics card either don’t use Photoshop CS5 or never work in CMYK but I’m putting this information out there for people who may see the same problem.

With current and recent drivers switching screen mode in Photoshop (the F key) causes the display of a CMYK image to go saturated/incorrect.
I always advise clients the F key is a great way to view your images against black or white as well as the default grey surround. The display of the image against black allows you to spot weak / grey shadows and against white allows you to check highlight areas as they would print on paper.
Unfortunately with recent Windows ATI drivers and Photoshop CS5 *and* CMYK images the colours within the image distort in the different display modes. This does not happen with an RGB image!
Because I prepare images for rerpo I do need to have accurate CMYK previews so have invested in a Nvidea GTX 550Ti card with 2GB of memory, this card does not have the same problem and its extra memory is a real bonus when opening lots of images in Open GL mode. It also has the advantage that I can use the Graphics card processors (Cuda cores) to help calculate and apply noise suppression using the latest version of Neat Image noise reduction.
When I first started using Neat image it took up to 60 seconds to process an A3/300dpi image, now with the help of the new video card this is reduced to a few seconds.
Reading round the edges it would appear that Adobe engineers are using HP workstations with Nvidea graphics cards when developing Photoshop, the card I have bought is quite modest (approx £100) but is sufficient for Photoshop, clients using Adobe Premier will benefit from a faster Nvidea card that will aid real time video rendering.
All a little sad really as I was more than happy with my ATI card till now, but its more important that I can trust my screen and that’s why I made the change.