This only occurs in photoshop (i.e. not in imageready), and only in colour palettes, images, etc. I have deleted my preferences, I have tried any number of colour spaces, etc. Nothing seems to work. Even my channels show up as brownscale rather than grayscale. See attached screenshots of this mess. Taking the screenshot captures the colour as the brown colour rather than the gray colour it's supposed to be, but photoshop still seems to be storing the colour as the right values (i.e. R 192 G 192 B 192 where if I screenshot it comes out as R 188 G 176 B 160).
When I save a file in photoshop, what should have been gray and was displayed as brown is successfully saved as gray which I can see fine in other applications.